Condition is something that is important to take into account when you're buying a collectible book. However, every collector, seller, and/or buyer judges condition a little differently, so in many situations it can be difficult to know exactly what you're getting.
When you're considering buying a book, take into account its rarity - could you find a copy of the same book in better condition relatively easily? - and the repairability of the damage. A cracked hinge is fairly easy to repair, if you have the skill, but a cover that's been scribbled on with permanent marker is much more difficult to fix.
The basic ratings of a book's condition are: Poor (P), Fair, Good (G), Very Good (VG), Fine, and Mint/Like New. Because condition is so subjective, you will also see ratings such as G+ ("Good plus") for books where the condition is better than Good, but not so good that the collector or seller is comfortable calling it Very Good.
|Poor (P)||A “reading copy” having signs of heavy use. It is very well worn and may have major soiling or binding defects. Cover may be damaged and may have loose joints, hinges, pages, etc. Usually books are only bought in this condition if they are particularly rare or inexpensive.|
|Fair||A worn book with defects such as a torn dust jacket, foxing, or loose binding, etc.|
|Good (G)||A complete book with no major defects, showing normal wear and ageing. Shorthand: G.|
|Very Good (VG)||A complete book, as issued, with very few blemishes or signs of wear. Shorthand: VG|
|Fine||Nearly new, with slight signs of aging, but no defects. This is the highest rating you'll see on a collectable book.|
In all cases, the more specifics you have, the better.
If you're selling a book, don't just say "Condition is Fair"; list what the damage to the book is, and provide sufficient photographs. Also, when you're grading a book's condition, if you're stuck between two grades, it's usually better to rate it with the lower one. That way, there's less chance you'll be accused of misrepresenting your item.
If you're buying a book, a seller who knows to list the specifics of the damage to the book, and who uses the correct terms for the damage, may be more knowledgeable or reliable than a seller who doesn't. Often, if a seller has proved they know what they're doing, a collector will buy from them based on their rating of the book alone. If you're new to collecting, you might want to consider asking a more experienced collector to recoommend a seller like this to you.
For a glossary of the various types of book damage and flaws, visit the HAS glossary of book terms.