I don't know what an 'isbn number' is.
In most (95%+) books it is a 10 digit (or in the last year or so 13 digit) number that can be found on the outside cover or more usually the inside page opposite the verso page (the one with the title and author in large letters at the beginning of the book) It may be hidden among the cataloging data that looks like an old card from pre-online catalog times.
ISBN, while not always unique, should exactly peg which exact title when the subject is known.
{Abe - for last sentence and for subtitle as per admin suggestion}
This message has been edited by anglagard, 05-11-2006 09:43 PM