So I recently came into a $50 amazon gift card, and want to put it into some drawing books.

Mostly been using free tutorials and following along youtube vids, but I'd like to get some physical resources, because I'm cool like that

Most of what I've been doing recently has centered around figure drawing and perspective, so any books that give a good mix of instruction, theory, and examples, would be much appreciated.

And any good drawing books in general outside of those categories would also be welcome suggestions.