I have a bookshelf of books next to me and the only ones with even slightly similar spines are books in the same series, not to speak of the covers.

I opened a couple of text heavy ones and they all had different font choices and minor variations on page layout. Most of them had elaborate and unique chapter headings.

Book typesetting is a fascinating subject, I would recommend anyone who works with websites to look into the way typography influences the reader's subconscious. (Maybe we'd have less Helvetica spaffed all over the internet!)