Some old books are valuable, some are just old! How do you tell? There are several factors which determine if a book is worth money to a collector. Here are some tips to guide you:
Age does not make a book valuable. At least , not age alone. Some books can be a hundred years old and not bring much, others need only be a few decades old to bring a nice return. The importance of what the book relates, it's physical condition, and demand also count for much. In general, when it comes to age, look for books printed before 1501, English books printed before 1641, books printed in the Americas before 1801, and books printed west of the Mississippi before 1850.
Condition is key! A book's physical appearance and its completeness make a huge difference. Is the binding tight? The cover intact? Pages clear? All these things a more will help determine value when rating a books condition. In general, the better a book's physical condition, the more it will be worth. A rating of "fine" is given to a book which is complete and shows very little or no wear. Loose pages or a worn cover will place a book in "poor" condition. There are "good" and "fair" ratings in between. Completeness, however, is KEY - missing pages or illustrations will make most books almost valueless.
Dust Jackets are vital. Virtually all books from the late 19th to today had one. And having it, in good condition, greatly increases the value of the book. As an example, if one searched records at Alibris for first editions of Harper Lee's To Kill a Mockingbird, you would find a "good" first edition/first printing for $6,500... without a dust jacket. For a copy in the same condition and printing, with a "good" dust jacket? The price sky rockets to $30,000! The major exceptions to whether a book had a dust jacket are the specially bound books, often limited editions. If a book is bound in real leather, there's a good chance it was not issued with a dust jacket, although it might have been issued with a slipcase, which is also important to the value of the book and should also be in good condition!
The contents of a book are also important. What is the books contribution? A major contribution was made to human understanding the first time Darwin's work was published. Jane Austin's books, they way her contemporaries found them, entice collectors today. First editions of these books would fall into this category. Apart from the first time the work was published, major changes to the work which significantly add to the contents can also make a book sought after. Illustrated editions, especially those by prominent artists, or titles with introductions by eminent contemporaries would be examples. Books that were banned or censored may be valuable because of their contents or even rarity, since few copies may have survived. Special binding or an innovative printing processes can make a huge difference. In general, markings, and inscriptions will be a problem and lessen the value of a book but there are exceptions; an autograph, inscription, or marginal annotations of a famous person can contribute to a book's importance and raise the value.
Rarity is a factor. As mentioned above, banned or censored books and books produced during certain periods or in particular places may mean that there are few available to collectors. As with other times, supply and demand is king! One can search the Internet on sites such as Bookfinder.com, AbeBooks.com, EBay, or ABAA.org to get an idea of how many copies of a book are being offered for sale. Auction sites can tell you how they are selling. Many booksellers have searchable catalogs and databases on their websites and these can be helpful in determining an approximate market value. Because the details can determine worth, pay close attention to the descriptions you find and make as close a match as possible. But remember, even if rare, if the condition or contents are negligible, it is likely to have little monetary value.
First Editions, when it comes to contemporary works especially, are important. The first time a book is published using the same setting of type (be it metal type, prototype, or camera-ready copy), is an edition. It may be an edition of 10,000 copies or 100,000 or more. If a book is popular, it may be reprinted over and over, with minimal changes, until demand is satisfied. This is a "printing". It is the First Edition, or the first set of books to "come off the press" which are the most sought. Information about editions and printings is usually included on the title page of a book or on the back (verso) of the title page. Without this information, the edition or printing is hard to determine and usually requires research. Collecting of true "first editions" of contemporary works has grown and raised the value of titles which are not especially old substantially. Writer's like Stephen King, Kurt Vonnegut, and JK Rowling find their first editions rising in value.
In some cases, even book club editions of titles can be collectible and of interest. For some authors and some editions, book clubs are preferable to paperback originals. For example, Danniel Steel fans like to collect the hard covers of her books, but the early ones were only available in paperback. If these are found, they're usually in pretty bad shape. For this reason the book clubs, which ordinarily go for from $2 to $5, may command prices from $8 to $15 and even a bit higher if signed. Some collectors insist on a copy of every edition, including BCEs, paperbacks, etc. Books from certain book clubs are also collectible. The Folio Book Society publications will always be collected. Collin's Crime Club (which was a different sort of Book Club) will always be collectable as long as people want to buy Agatha Christie firsts. In general, hwever, the book clubs do NOT command that much of a price (about equivalent to collectable paper backs).
A "limited edition" can be valuable, depending on the book and how limited it is. Again, rarity can come into play. The term is reserved for editions where copies have an explicit "limitation statement" which contains information on the number of copies printed, and usually a breakdown of how many copies were printed on a certain type of paper, or bound in a certain kind of binding, or reserved or withheld from sale. The statement is usually found on the back of the title page or on a separate page at the beginning or end of the volume. The number of the specific copy is often printed or added by hand (as in "no. 46 of 500"). The lower the number of the copy, the more valuable. If accompanied by the autograph of the author(s), publisher, or other contributor, so much the better! Whether looking at first or limited editions, the size of an edition does not by itself determine a book's value, or even its rarity. Other factors play a part.
Provenance or ownership can improve a book's value, if that person is important or famous and if the book held significance for him or her. Autographs, inscriptions or dedications, bookplates or stamps, or other distinctive markings can be proof of ownership, but they can also be forged. Authentication is important.
To promote sales and for charity, contemporary authors routinely sign copies of their books. Because these are common, modern autographs usually add little value. However, "presentation" or "association" copies, those signed on special occasions, or inscribe and presented to important associates and friends may greatly increase the value of a title. "May" is the key word here - expertise in the current market is needed to make a valuation of this.
So, do you have old books? Or valuable books? The book collecting market is like any other collectible market, constantly changing. Authors go in and out of favor; time periods and type styles became popular and then fade. You need to remember that books, as with any other collectible, are only worth what someone is willing to pay for them. Doing a little research and being honest to yourself about your items will save you space, time, and maybe make you some money!