Actually I think we don't need a DB but just a table somewhere on the site with the list of books available. At least until we have so many books available that we need a DB to list them.

Plus I think each book in the Book Reviews section lists the ISBN, so you can probably get it from vroom.

If you really want an ISBN search I found there a search thingie that retrieves the title for a given ISBN, It found the Camel 3, but then the tool went down before I had a chance to test it further :--( I'll keep you posted on whether it also works for less common titles as soon as it comes back).

Update: the store seems to have a good collection, they had the Camel 3, Web Client Programming with Perl, the MySQL book by Paul Dubois and the XSLT book. They just missed a Unicode book that's about the most arcane book I own.