The (very rough and basic) ‘catalogue’ I recently created already had a link to Google Books for each item. This was just a very simple URL with an ISBN stuck on the end, e.g. http://books.google.com/books?as_isbn=0596003722
Tonight I have made the first steps in adding links to items using the Google Books API using both the static (simple) and dynamic methods.
You can see an example here http://www.nostuff.org/tdn/6b/item.php?item=0596003722.
You can also do a search via http://www.nostuff.org/tdn/6b/
The layout is currently very rough, and the dynamic search is broken in that it will only show a result for the first ISBN for a given item (I know why but don’t have time to fix now).