Well, it's probably best if you read Alice's Adventures In Wonderland first, if ya haven't already. Through The Looking Glass is kinda like the sequel to that one. The first book is a lot more famous than the second, but if you ask me the second book is just as good. They're both about this girl named Alice who ends up in another world, first by falling through a rabbit hole and then in the second book by going through a mirror. ... Or, you know, a looking glass.