You can do book searches on Book Finder - Super Site -- http://www.bookfinder.com"
The point of the Bookfinder website is that you can find USED CATHOLIC Books in very good condition for anywhere from $3 to $6 for something that might cost $25. You can also find hard to find books as well.
The BOOKFINDER site does not just check AMAZON, but quite a number of sites -- ABEBOOKS, ALBRIS, etc.