I am absolutely in love with "big ideas simply explained" series now!
Look if you want to know almost everything about a subject this book isn't for you. Each of these books talk about a subject as you know, and gives you a really tiny brief information on that subject. so for example after reading The Mythology Book you can tell myths from which culture are your favorites and THEN you can research and find out more stuff about that. these series only gives you a general idea about each subject, and of course they can't talk about everything in detail.
so i would call them "big ideas briefly explained" :D