Posted By:
AnonymousABE and Alibris....
Two of the better online search sites for old books. All books.
Tens of thousands of booksellers worldwide list books... it is great if you're a bibliophile!!!
http://www.abebooks.com/
http://www.alibris.com/
If you're looking for a used book, these places are fantastic. A few times I've seen a book on eBay, bid, get outbid, rebid, outbid again... by now the price is working its way up there, I check on ABE and bingo, there's the book for half of what it is on eBay, and they'll ship now, rather than after the auction ends.
If your spouse is mad because you have stacks of books all about the house, then you might need to stay away from these sites.