Buying signed rare books is a relatively simple endeavor, especially since many sellers will have their collections available to browse and search online. If you're hoping to find a signed edition by a favorite author, or simply to add weight to your collection, here are three things to consider:
Is the Signature Authentic?
If you're not buying the book at a shop or fair in person, there will hopefully be a photograph of the signature/inscription available to view online. If not, keep an eye on the listing - a copy is the name only, signed onto, 'inscribed' is a note written by the author, and confusingly 'autographed' means that the book was hand-written and does not refer to a signature or inscription at all.
As you can imagine, it can often prove easier to verify the provenance of an inscription, as it will add significant context to the book. A signature in and of itself, while very often cherished by collectors, is less easy to confirm as being real.
Authenticity is, therefore, a vital concern. To protect against the possibility of fraud, one may consider buying books from accredited sellers who are members of various respected bookselling associations. Examples of these include the ABA, the ABAC, the ABAA, and the ILAB - for a full list, visit the Biblio trade association page here.
What kind of Inscription is it?
Inscribed by J.K. Rowling
You'll often see certain terms used to describe what kind of inscription is inside the book. If a book is simply listed as 'inscribed by author', it is a general inscription to another person, not necessarily of particular note or for a specific reason. Presentation copies however are specifically gifts from the author, and because they're intended as such are likely to be signed very close to the publication date of the book. Dedication copies, meanwhile, are particularly special, inscribed to the same person that appears on the printed dedication within the work.
How Rare is the Signature?
When keeping an eye on listings for signed and inscribed books, it's helpful to know how prolific in his or her signings an author was. The likes of Winston S Churchill signed a large numbers of books, for instance, and therefore it is not only easier to find them for sale, but less expensive to purchase them too. Meanwhile, authors like J.D. Salinger and Thomas Pynchon were and are notoriously reclusive, and therefore signed first editions by either writer will fetch a great deal.
In some cases, an author's approach to signing can change over time - after an initial flurry of dedications, J.K. Rowling became increasingly reticent to sign books. Now, due to the extreme levels of attempted fraud associated with her signature, a holographic sticker will accompany more recent authentic signed copies. Make sure you do your homework on the specific author to better determine how valuable a book could potentially be.