Most book dealers use a set of standardized terms in describing the condition of a book. The terms infer the overall condition of the book but the description should also state any obvious important flaws or variances from the term. Always feel free to ask for more details if you're uncertain about a book's condition.
As New (or "mint") - refers to a book or magazine that is in pristine condition. If issued with one, the dustjacket is flawless and without smudges, scuffs, or tears. The book is without marks or stamps, has no bent or missing pages and is structurally perfect.
Fine - refers to a nearly perfect book which approaches "as new" but has one or more minor flaws or shows very slight wear.
Near Fine - approaches fine but shows more signs of handling or wear. Variance from the "fine" condition, such as small tears and wear to the dustjacket, previous owner's name in pencil or ink or on a bookplate, and price clipped from the dj flap should be described.
Very Good - the book shows limited wear but its physical condition is above that of the average used book. Any stains or marks, small tears or creasing should be noted.
Good - describes the average used book which shows its age. A good book makes an adequate "reading copy," but is not of the quality sought for a collection.
Fair - the book has seen hard use and, unless rare, has little value other than as a reading copy. It may have damaged or missing pages or endpapers, heavy underlining of text, stains or spotting.
Poor - the book's condition is far below that of the average used book and has obvious damage.
Book Club Edition or BCE - although book club editions may be in excellent condition, they are ordinarily not deemed collectible. They are an excellent choice as a reading copy.
Ex-library - may also be in excellent condition but was purchased from a library. Generally includes the library's stamps or other marks and are sometimes bound differently.