Well it uses the Amazon API for all the database calls.. I figure they would have a decent database I could not find any other databases that I could use that were even close to that size..
Well one of my original ideas was to allow for manual entry for books that were not in the database.. But I did not think most people would want to enter in all the details for every book they had
If you don't mind, would you take one of the ISBNs (for a book not found by my site), and see if Amazon can find it by the ISBN number?
If it finds it there, maybe my code has a bug, since it should have everything Amazon has.