What book(s) on comparative mythology would you recommend to a beginner?

To be honest, I’ve not read a book on comparative mythology that I’ve liked all that much.  It’s a good idea in principle but one that lends itself to overreaching, and making some strange comparisons between cultures that have little in common.  Actually, you’ll probably not do yourself a huge disservice by just bingeing a few Wikipedia articles, and as a university teacher I’m not supposed to say that but, well, it has a mix of the actual content of myths and interpretation of them, and can generally point you to respectable books and articles that will tell you more if you’re interested.  Just don’t take anything it says on the interpretive side as the gospel truth, and you’ll be fine.