Okay, this isn't an astronomy textbook, but in a quick and easy to read volume, Gardner provides some clear explanations of some interesting puzzle like questions. No previous knowledge is assumed, so the book will be a bit easy for the serious astronomer, but I don't believe that's whom the book is intended for. In fact, I'd recommend buying it for an interested middle schooler or high school student to stimulate their interest int he solar system. Very entertaining, quick and easy to read with some complicated problems explained.