For collectors, remaindered books are not as valuable as books that have not been remaindered, but most casual readers can't tell the difference between remaindered and non-remaindered books. Remaindered books can range from books that appeal to very small markets, such as specialty cookbooks, to best-sellers that bookstores over-ordered.
Remainder marks vary from publisher to publisher and from bookstore to bookstore. Most bookstores simply draw a black line across the top edges of the book's pages. Some publishers, including Random House and Simon & Schuster, stamp the edges with their logo. Other marks include lines in green, red or another bright color.
Some remainder marks are not so easy to spot. Older books, particularly those from the 1980s and earlier, often have had the edges of their pages sprayed with dye in dark blue or purple.
If you are selling a book with a remainder mark on it, state that in your description or point it out to your customer. Many people won't mind, but some collectors won't buy books with remainder marks.
If you are a collector, you will want to avoid buying books with any remainder or other marks on them. Remainder marks lower the value of a collectible book, even if it is in otherwise perfect condition. If you are buying a book just for your own reading pleasure, remainder marks make no difference--your book is the same inside and out as a full-priced, non-remaindered copy.