@smudges – to the question of why there are sometimes extra blank pages at the ends of books – it has to do with their printing method manufacturing.
See this:
What is a book signature?
A signature, sometimes abbreviated sig, is a sheet of paper printed with four or more pages and folded one or more times to the approximate size of one page and in a manner which puts the pages in proper numbered order. The more common signature impositions are 4, 8, 16, 32, and 64 pages, which are formed by folding the sheet in half one or more times. Less common are 12, 20, 24, and 36 page signatures, which require more complicated folding patterns.
In some regions, signatures are identified by their lowest page number, so the second signature in a two section, 16 page book might be called “sig 5,” because it begins with page 5. In recent years, and what we do here at Carter Printing, signatures are identified by their position in the book, so the example might also be called “sig 2.” The cover of the book is not considered a signature in any numbering scheme. From Latin signum, sign.
So if there are extra (unprinted) pages at the end of a signature, they’re added, because of the process.