The age of a book has little to do with its value; in fact, today's collectible market seems to be more interested in modern books than in the classics. So... what makes a book valuable?
Let's say you have a title that is desirable to collectors, and you've heard that someone else sold a copy for $1,000! Here's some basic information on ascertaining if you have a $1,000 treasure or a $20 reading copy.
Note: The following pertains to American publishers and printing.
If a book is a desirable title to collectors, then the issues of edition and condition become important. Most collectors want the first edition (also called first printing) of a title. Significant authors may also be published in limited or special editions, perhaps with a special deluxe binding, signed by the author and limited to a small number printed. These are usually collected also, although marketplace demand governs which can command a premium price.
So, how can you tell if you have a first edition? Although publishers are not standardized in their identification methods, most of the well-known publishers of modern books follow conventions that are found on the copyright page. The copyright page is the back of the title page, and it specifies the copyright owner and date. Other information is provided on the copyright page, but we're interested in finding a number row near the bottom of the page. For most publishers (except Random House) who use a number row, if the single character 1 or A appears in the row, it is a first printing. It may appear at the beginning or the end of the row.
1 3 5 7 9 10 8 6 4 2
10 9 8 7 6 5 4 3 2 1
1 2 3 4 5 6 7 8 9 10
all identify first printings. Many publishers also include the words "First edition" or "First printing" as well.
Be careful -- later printings may still have the words "First Edition" while the number row indicates a later printing. The lowest number in the row shows which printing this copy is. If the lowest number is a 3, then you have a third printing (of no particular value).
The exception to the rule -- there's always one, isn't there? Random House. Random, if they use a number row, indicates a first printing with the number 2 AND a statement of First Edition.
Earlier this century (and sometimes today), publishers did not use the number row. They simply printed a date on the title page and did not specify any later printings on the copyright page. Usually, if the copyright date and the date printed on the title page match, you have a first printing.
The next critical issue with regard to value is a book's condition. Collectors want the best condition they can get; if a book has never been opened, so much the better. The best collectible condition is a pristine book, very crisp, with no previous owner's bookplate, name, markings, or dog-eared pages.
If the book was issued with a dust jacket, the jacket must be present and in pristine condition also -- not price-clipped, not taped to the book, not creased, rubbed, wrinkled or torn. No pieces missing or little chips gone ... you get the picture.
Today, most of the large retail publishers print the book's price on the dust jacket flap. If there is no price, the book may be a Book Club edition of no value. However, there are some university presses who do not print the price on the dust jacket.
This may seem odd, but in today's market the dust jacket contributes as much as 75 - 85% of the value of the book.
Never remove or destroy a dust jacket ... even if it's in bad condition. Because of the fragile nature of dust jackets, many of them don't survive. Collectible books from the earlier years with dust jacket (even chipped and torn) are frequently worth 2 to 3 times the same book without a dust jacket.
So, cover your dust jackets with clear mylar covers (made for the purpose) and then keep the jackets on the books. They protect books from dirt and oil and were designed to protect a book's covers.
When you read a book catalog or describe a book that you wish to sell, there are some widely accepted standards for grading the book. These grading standards should be applied separately to book and dust jacket; for example, fine/very good means that the book is fine and its dust jacket is very good. In addition to grading the book and its jacket, you should also detail all flaws.