A Lifetime Guarantee. No Fine Print.
We stand behind every book we sell with an unconditional, lifetime money-back guarantee on authenticity — and 10% of our revenue goes to childhood cancer research.
The Guarantee
Our guarantee is simple and absolute:
If any recognized authentication service refuses to certify a signature on a book purchased from Cervantes Rare Books, we will refund the full purchase price. This guarantee has no expiration date. It applies for the lifetime of the buyer and is transferable to subsequent owners.
We do not offer this guarantee as a marketing tactic. We offer it because we are confident — deeply, professionally confident — in the authenticity of every signature we sell. We have staked our reputation and our livelihood on the accuracy of our authentication. The guarantee is simply the logical expression of that confidence.
Letter of Authenticity
Every book sold by Cervantes Rare Books ships with a comprehensive Letter of Authenticity. This is not a generic certificate with a hologram sticker. It is a detailed written document that includes:
- Signature Analysis — A description of the specific features examined and why we believe the signature is authentic.
- Known Provenance — All available information about the book's history and chain of ownership.
- Edition Details — Full bibliographic description including edition, printing, publisher, and date.
- Condition Report — Honest, detailed assessment of the book's physical condition, following standard antiquarian grading.
- Professional Opinion — An extended narrative opinion from the authenticator, addressing any features of particular note.
This document is signed by John Kowalski, PhD. It is not an anonymous rubber stamp. It is a personal, professional assessment from someone who will answer questions about it next week, next year, or next decade.
Why We Believe Certificates Have Failed
The authentication certificate, as it currently exists in the collectibles market, is a relic of a simpler era. It was designed when forgeries were crude and forgers were few. In that context, a stamp of approval from a known house carried meaningful weight.
Today, certificates are issued at industrial scale by houses whose business model depends on volume. An authenticator who processes dozens of items per day across thousands of different signers cannot provide the depth of analysis that modern forgeries demand. The certificate becomes a formality — a reassuring piece of paper that obscures rather than reveals the quality of the analysis behind it.
Worse, the certificate system creates a perverse incentive. Once a fake acquires a certificate, it becomes nearly impossible to challenge. Subsequent buyers treat the certificate as proof rather than opinion. The fake circulates indefinitely, protected by a piece of paper that was itself the product of a thirty-second examination.
Our Letter of Authenticity is our answer to this problem. It is transparent, detailed, and accountable — and it is backed by the only guarantee that matters: your money back if we're wrong.
Preservation Standards
A rare book is a physical artifact. Its value depends not only on its bibliographic significance and the authenticity of any inscriptions, but on its physical condition. Preservation is not an afterthought — it is a fundamental obligation.
All books in our inventory are stored in a purpose-built, climate-controlled facility in Valencia, Spain. The environment is regulated for:
- Temperature — Maintained within a stable range to prevent thermal expansion and contraction of bindings and paper.
- Humidity — Controlled to prevent foxing, mold, warping, and other moisture-related damage.
- Air Quality — Filtered to minimize dust accumulation and exposure to pollutants that accelerate degradation.
Books are handled with appropriate care and stored upright or flat depending on their format and condition, using archival-quality materials throughout.
Shipping Standards
Every book we ship is packaged using professional-grade materials designed to protect objects of significant value during international transit.
All shipments are fully insured for their sale value. We ship internationally to the United States, the United Kingdom, and throughout the European Union.
Packaging methods are tailored to the individual book's format, condition, and value. High-value items receive custom packaging solutions that exceed standard industry practice.
We provide tracking information for all shipments and are available to answer questions about shipping timelines and logistics.
Why Authentication Adds Value to Your Books
A signed first edition without proper authentication is a liability. When you eventually sell the book — or pass it to heirs — the next buyer will demand proof that the signature is genuine. Without a credible Letter of Authenticity, the book's signed status becomes an unverified claim rather than a documented fact, and its market value drops accordingly.
Authentication protects your investment
Books purchased from specialist dealers with lifetime guarantees consistently outperform those acquired from unverified sources. The authentication documentation travels with the book, providing every future owner with the confidence they need to pay fair market value. Our Letter of Authenticity is not a disposable certificate — it is a permanent record of professional assessment that enhances the book's provenance and desirability.
A guarantee reflects the dealer's confidence
Any dealer can claim a signature is authentic. Only a dealer with genuine expertise will back that claim with a lifetime money-back guarantee. When we guarantee a signature for life — with no expiration date and no fine print — we are telling you exactly how confident we are in our own authentication. That guarantee is transferable: if you sell the book, the new owner inherits the same protection. It is the strongest possible signal that the dealer believes in what they are selling.
The cost of unauthenticated books
Collectors who buy unauthenticated signed books often discover, sometimes years later, that they paid a premium for a forgery. The emotional and financial cost of this discovery is significant. Worse, the secondary market for unauthenticated signed books is thin — knowledgeable buyers will not pay fair value for a signature that lacks credible documentation. Investing in proper authentication upfront is always less expensive than discovering the problem later.
Giving Back: 10% of Revenue
We donate 10% of our entire revenue — not profits, revenue — to the National Pediatric Cancer Foundation through the eBay for Charity program. This is not a seasonal promotion or a one-time gesture. It is a permanent commitment applied to every book we sell.
The money is sent directly by eBay — ensuring full transparency and eliminating any possibility that funds are diverted or mishandled.
We chose the National Pediatric Cancer Foundation because of their singular focus: the Sunshine Project, an innovative collaboration bringing together the nation's top doctors and researchers with one goal — to find a faster cure for pediatric cancer. Their research produces less toxic, more effective treatments through clinical trials that benefit children not only in the United States but globally.
"Every book you purchase from us directly funds research to eliminate childhood cancer. We believe that dealing in objects of cultural significance carries a responsibility to give back — and we have chosen to honor that responsibility with the largest commitment we can make."
— John Kowalski, PhD, Founder of Cervantes Rare BooksNational Pediatric Cancer Foundation — EIN: 59-3097333 — eBay Charity ID: 121164 — Learn more about eBay for Charity
Authentication, Estate Planning & Your Collection's Future
A signed book collection is a legacy. Whether you plan to hold your collection for decades, pass it to children, or eventually sell it, the quality of your authentication documentation determines how smoothly that transition goes — and how much value is preserved.
Why heirs need authentication documents
When a collection passes to heirs who may not be experienced collectors, proper authentication documentation is essential. Without it, heirs may sell books at a fraction of their value — or fall victim to unscrupulous buyers who claim signatures are unverified. Our Letter of Authenticity and transferable lifetime guarantee protect your heirs by providing professional documentation that any buyer or appraiser will recognize.
Insurance and appraisal considerations
Specialized collectibles insurance requires documentation of value and authenticity. Our Letter of Authenticity satisfies both requirements — it identifies the book, confirms the signature, and establishes provenance. We recommend refreshing appraisals every 3–5 years and storing documentation separately from the collection. Contact us anytime for updated market valuations of books purchased from us.
The transferable guarantee advantage
Our lifetime guarantee is transferable to any subsequent owner. This means that when you sell a book or pass it to an heir, the new owner inherits the same protection. This transferability adds measurable value to your books — a signed first edition with a transferable lifetime guarantee from a specialist dealer is worth more on the secondary market than one without.
Questions About Our Guarantee & Authentication
How does your lifetime guarantee actually work?
Our guarantee is simple: if any recognized authentication service refuses to certify a signature on a book purchased from Cervantes Rare Books, we refund the full purchase price. There is no time limit — the guarantee lasts for the lifetime of the buyer and is transferable to subsequent owners. To make a claim, contact us with the authentication service's findings and we will process the refund promptly. In our history, we have never had a guarantee claim, because we are deeply confident in every authentication we make.
Is your guarantee transferable if I resell the book?
Yes — our lifetime guarantee is fully transferable. If you sell a book purchased from Cervantes Rare Books to another collector, the new owner inherits the same guarantee. This transferability adds tangible value to your purchase, because it means the book carries our authentication and protection for its entire lifespan, regardless of how many times it changes hands. The Letter of Authenticity that accompanies the book serves as the guarantee document.
What counts as a 'recognized authentication service' for guarantee purposes?
We interpret this broadly in the collector's favor. Recognized authentication services include the major third-party houses (PSA, JSA/James Spence Authentication, Beckett Authentication Services), established rare book dealer associations (ABAA, ILAB members), and credentialed forensic document examiners. If there is any ambiguity about whether a specific service qualifies, we resolve it in favor of the buyer. Our goal is not to create loopholes — it is to stand behind our work completely.
What is included in your Letter of Authenticity?
Our Letter of Authenticity is a detailed, multi-page document that includes: a signature analysis describing the specific features examined and why we believe the signature is genuine, known provenance documenting the book's history, full bibliographic description (edition, printing, publisher, date), a condition report following standard antiquarian grading, and an extended professional opinion signed by John Kowalski, PhD. This is not a generic certificate with a hologram sticker — it is a transparent, detailed, accountable assessment.
Why do you think authentication certificates from big companies are failing collectors?
The major authentication houses were designed for volume — certifying thousands of items per week across tens of thousands of different signers. An individual authenticator may handle sports memorabilia, entertainment autographs, and literary signatures in the same day. They spend seconds to minutes per item and rely on quick pattern matching against limited reference material. This model was adequate when forgeries were crude, but today's sophisticated forgers can produce signatures that pass a brief inspection. Only deep specialization — studying hundreds of signatures by the same author — provides the intimacy needed to catch modern fakes. Read our full analysis.
Do I get eBay buyer protection in addition to your guarantee?
Yes. Because we sell through eBay, every purchase is covered by eBay's Money Back Guarantee in addition to our own lifetime guarantee. This means you have two independent layers of protection: eBay's standard buyer protection for any transaction disputes, and our lifetime authentication guarantee that extends far beyond eBay's coverage period. This dual protection is one of the reasons we chose eBay as our primary sales platform.
What happens if you go out of business — does the guarantee still hold?
We have structured our guarantee to be as robust as possible. The Letter of Authenticity itself serves as a permanent record of our professional assessment, and its value as a provenance document does not depend on our continued operation. That said, we are committed to longevity and sustainability. Our 10% revenue donation to charity, our deep investment in inventory and expertise, and our reputation in the collector community all reflect a business built for the long term, not for quick profits.
How does proper authentication protect my investment in signed books?
A signed first edition without credible authentication is a liability. When you sell the book — or pass it to heirs — the next buyer will demand proof. Without a detailed Letter of Authenticity from a recognized specialist, the signature becomes an unverified claim, and the book's market value drops to unsigned levels or below. Books purchased from specialist dealers with lifetime guarantees consistently outperform those from unverified sources. Our authentication documentation travels with the book permanently, providing every future owner with the confidence to pay fair market value. Read our complete collecting guide.
Buy With Absolute Confidence
Every book. Fully authenticated. Lifetime guarantee. 10% to charity. No exceptions.