Back in 1949, the trade magazine AB Bookman's Weekly tried to address this issue by providing a standard by which used and rare books could be described. Over the years, these standards have been refined and have become a shorthand way for booksellers to quickly describe a book's condition.
Unfortunately, this shorthand means nothing if the buyer does not know how to interpret it. Additionally, general terms for describing book condition such as "Good", "Very Good", "Fine" and so on have become increasingly subjective. Traditionalists often cite this as a significant drawback to the buying and selling of books on the Internet.
But the solution to the problem lies in understanding the shorthand code of book descriptions. While the basic information set off in quotes comes from the original AB Bookman's classifications, the comments following the AB Bookman statements are my personal interpretations and should be considered as my opinion. Please be sure you ask enough questions when buying 'sight unseen'.
"As New is to be used only when the book is in the same immaculate condition in which it was published. There can be no defects, no missing pages, no library stamps, etc., and the dustjacket (if it was issued with one) must be perfect, without any tears." (From the old AB Bookman's Describing Condition)
Little needs to be added here. Most collectors note that even an Authorial signature or inscription disqualifies a book from being listed as "As New" because the book is no longer in the same condition as it was the day it rolled off the press. Such signed, unread books are often-times graded as 'very fine'.
"Fine approaches the condition of As New but without being crisp. For the use of the term Fine there must also be no defects, etc., and if the jacket has a small tear, or other defect, or looks worn, this should be noted." (From the old AB Bookman's Describing Condition)
This classification applies in cases where the book may lack a certain "crispness" to qualify for the "As New" grade but is otherwise nearly flawless. Flaws must be minute and called out. If there are any flaws whatsoever, many dealers will downgrade to Near Fine.
Near Fine or Very Good Plus
These are not AB Bookman's terms, but are frequently used by many dealers to grade a book that appears to have been carefully read, but may have minor flaws which keep the book from being Fine. The flaws will usually be subtle, often requiring closer inspection to see.
"Very Good can describe a used book that does show some small signs of wear - but no tears - on either binding or paper. Any defects must be noted." (From AB Bookman's Describing Condition)
Fairly self-explanatory. If there are signs of reading, it was a careful reading. Any flaws of note will be called out. Oftentimes books that come from a smoking environment, even if Fine or Near fine other wise, are graded as Very Good, just because of the degradation of the paper itself.
Very Good Minus
Here is another non-"AB Bookman" term. Typically, a very good minus book will exhibit signs of reading and wear, which will be noted in the description. Further clarification of the book description should make clear why a book is rated as very good minus.
"Good describes the average used and worn book that has all pages or leaves present. Any defects must be noted." (From AB Bookman's Describing Condition)
One important thing for the beginning book collector to note is that a book graded "Good" really isn't that good. A "good" book should be considered only as a place-keeper in a collector's library. Strive for Very Good or better for your collection.
"Fair is a worn book that has complete text pages (including those with maps or plates) but may lack endpapers, half-title, etc. (which must be noted). Binding, jacket (if any), etc. may also be worn. All defects must be noted." (From AB Bookman's Describing Condition)
A self-explanatory rating.
"Poor describes a book that is sufficiently worn that its only merit is as a Reading Copy because it does have the complete text, which must be legible. Any missing maps or plates should still be noted. This copy may be soiled, scuffed, stained or spotted and may have loose joints, hinges, pages, etc." (From the old AB Bookman's Describing Condition)
A poor book has no merits as a collectible volume but can be a good reading copy.
"Ex-library copies must always be designated as such no matter what the condition of the book." (From the old AB Bookman's Describing Condition)
Book Club Edition
"Book Club editions must always be noted as such no matter what the condition of the book." (From the old AB Bookman's "Describing Condition")
In most cases, Book Club editions are not of value to serious collectors. There are many small houses, however, which publish very nice limited editions. These editions are by definition, not true first trade editions, so beginning collectors must determine for themselves what they wish to collect and why.
"Binding Copy describes a book in which the pages or leaves are perfect but the binding is very bad, loose, off, or nonexistent." (From the old AB Bookman's Describing Condition)