I just came across this really nice website about bookbinding structures and styles from the Special Collections in the Princeton University Library:
I think it is remarkably well done, comprehensive and well documented. It was made after an exhibition was held from November 10, 2002 through April 20, 2003, entitled “Hand Bookbindings: Plain and Simple to Grand and Glorious“. The photos are definitely a plus and it’s possible to magnify the pictures quite well. I particularly like the page about binding waste, as it relates so well to the Derry and Raphoe Diocesan Collection with its many manuscript-wastes re-used in bindings.
Any book-lover would want to spend time on that website and I just wish I was in Princeton while this exhibition was held!