http://www.wildandwoolley.com.au/self_publish/getting_started this website shows the different book sizes. I know we aren't using these, but at least we know what the traditional ones look like.

http://www.writersservices.com/wps/s1_book_sizes.htm This website is very good as it explains the whole process of book production from pre production, printing, design, marketing etc. Click the options on the side.

http://www.viovio.com/wiki/index.php?structure_id=473 This website shows different types of square books so we can base our book size on one of these perhaps. It also has different binding options too