To the high-paying collectors, "condition is everything" unless the book is so rare that a copy in good condition is unobtainable. If you are not experienced in determining the correct (although always subjective) way to describe a book's condition*, you will need to take the books to someone who can look at them. A good used-book dealer in your area should be able to help you determine the values, or direct you to someone who can. If you are interested in selling the books, ask the dealer to make an offer. Since the dealer must pay overhead costs and assume all the risk, the price quoted to you should be one-fourth to one-half of what he or she expects a buyer to pay. If the books are valuable, the dealer may be willing to take them on consignment at an agreed-upon percentage (25% to 50%).

       For many years, the grading system defined by AB Bookman (now sadly defunct) was the standard in the antiquarian book trade. IOBA's standards, listed below, do not fundamentally differ from those standards though they have been expanded upon, and defined a bit more specifically.
 
(Condition normally shown as __/__, i.e., F/F, denoting first book & then dustjacket condition.)
AS NEW (AN) or VERY FINE (VF) or MINT (M): Without faults or defects, unread, in the same immaculate condition in which it was published (Note: very few "new" books qualify for this grade, as many times there will be rubs/scuffs to the dustjackets from shipping, or bumped lower spine ends/corners from shelving).
FINE (F): Approaches the above, but not crisp. May have been carefully read and dustjacket may have been slightly rubbed or spine ends slightly bumped from shelving/shipping, but no real defects or faults.
(NOTE: From here on, there may be "+" and "-" in a grade, which will mean that it is above the grade noted but not quite to the next higher grade for "+", and that it is below the grade noted but not quite to the next lower grade for "-".)
NEAR FINE: Also used, although not contained in Bookman's Weekly definitions, meaning a book or dustjacket approaching FINE but with a couple of very minor defects or faults.
VERY GOOD: A used book showing some small signs of wear on either binding or dustjacket. Any defects/faults must be noted.
GOOD: The average used and worn book that has all pages or leaves present. Any defects must be noted.
FAIR: A worn book that has complete text pages (including those with maps or plates) but may lack endpapers, half-title page, etc. (which must be noted). Binding, dustjacket, etc. may also be worn. All defects/faults must be noted.
POOR or READING COPY: A book that is sufficiently worn that its only merit is the complete text, which must be legible. Any missing maps or plates should still be noted. May be soiled, scuffed, stained, or spotted, and may have loose joints, hinges, pages, etc.
EX-LIBRARY: Must always be designated as such no matter what the condition of the book.
BOOK CLUB: Must always be noted as such no matter what the condition of the book.
BINDING COPY: A book in which the pages or leaves are perfect but the binding is very bad, loose, off, or non-existent.
Always, if issued with one, the lack of a dustjacket or slipcase should be noted.
Copyright 2000 by Independent Online Booksellers Association
 
       If you decide to sell books yourself, you will also need to buy & study copies of A Pocket Guide to the Identification of First Editions Amazon.com, Alibris and Points of Issue Amazon.com, Alibris both by Bill McBride, to help you determine whether any of your books are first editions. Remember that to a collector the "first edition" means the first printing , which is not always easy to determine, since each publisher uses a different system or systems to indicate a first printing. Even the statement "First Edition" is no guarantee.
       There are printed books that give book values, but they are expensive and quickly go out of date. They do have some value in that if you find your book listed there, you know it is a "collectible" book. Try a used book store to find any of these, and ask the bookseller for advice.
       To determine values via the internet, I search for the matching title among the used-book web sites listed at Search for Books with Rising Dove. I compare the condition of my copy to the one described. For more help on determining the condition of your book, I recommend Glossary of Book Terms.
       Here is more information on the different types of first editions.
       Another trick is to check auction sites for matching titles. Make sure you check the listings of *completed* auctions; the dealer's asking price may be simply wishful thinking, but the price someone has actually paid is a true indicator of what someone else is likely to be willing to pay.
       If you want to get the books to a safe place quickly, and still make some money, try donating them to a University Library. They should be willing to have the books appraised, (although you may have to pay the appraisor's fee, which can be steep if the book is valuable), and to help you with the paperwork necessary for getting a nice tax deduction.
       Unfortunately, I no longer have time to offer free help in estimating the values of books. There are others who will do so for a fee. One example is http://www.booksappraised.com. (I do not know this person.) I'm willing to do so myself for a fee, of couse, but I'm not licenced to do it, so you might prefer to pay a bit more and go with someone who is.