If you are trying to value your own copy of a book, it is extremely important that you understand why some books that seem very similar can have enormously different prices. They're only valuable if somebody wants to buy them.
Collectors are only interested in certain books.
If copies exactly like yours are common, they'll be worth a lot less money than if they're rare. The value of one edition of a book will have very little to do with the value of another edition, or even a different printing, of the same title. One copy of the first printing of the first edition of a particular title can be worth over ten times as much as another copy, if the first copy is as new in dust jacket, with an inscription by the author and the second copy is a worn ex-library book with a bad binding. Serious book collectors frequently don't ever actually read the books they buy to form part of their collection. Most used book dealers specialize.