http://www.fetchbook.info

This site is great!! It will give you all the listing sites for the particular book you are looking for and by alphabetical and price order, including new and used books.

I just stumbled on it today looking for an Apache Server book and it's great. I did a few other test searches for old books and lo and behold, I found them all and several. I'd say this site has the best database for book searching that I've found so far.

You can compare prices and you can read customer reviews and each book listed is linked to the site that sells it. Yahoo!!