First editions are most valuable. Any books autographedc by the author are valuable. I have a friend who collects first editions, even first editions of magazines.

Look in the Yellow Pgs under bks and find ones listed as either 'rare' bk dealers, or something other than the usual chain stores (which may not have knowledgable staff) and ask about your books. Also I think if you Google 'signed book values' you may get sites that let you input titles and get answers.

You can also look on Alibris or Abebooks to see how a similar first edition copy of your book is priced. This would at least give you a ballpark idea of what it might be worth.

Modern firsts are something with a huge percentage of the value being for mint-condition books, with perfect, original, Mylar-protected dust jackets. For everything else, even first editions, there is a much more modest value.

First edition Hemingway and you're really in luck; first edition of one of the current mystery or thriller authors, well, you may be in luck if it's an early work by the author (when fewer were printed) but not if it is a FE of a later work when every Borders and B&N sold hundreds of copies of the first printing of the edition.

And of course, first editions of the book club runs aren't worth anything.

You can check all the used book sites at once by going to www.addall.com. Sort the results by price in ascending order, or descending, as your personality requires. And remember those are asking prices to buy the books, not to sell the books. EBay final bid prices are much lower in most cases.

Depends--do you have the dustjackets? Book club first editions aren't worth anything.