There are four good things about these books by Charles Rivers Editors: 1) They are usually brief, 2) They do provide a good overview of a particular topic, 3) They usually have a decent bibliography and 4) They can usually be got for free.
This book does a good job of describing what the ancient sources say about the Hanging Gardens. It also details the mystery of what the Gardens looked like and whether or not they actually ever existed. The most fascinating part of the book was the time devoted to the theories of Stephanie Dalley, who has postulated that the Hanging Gardens were mistakenly attributed to the Neo-Babylonian city of Babylon but are more likely to have been in the Assyrian capital of Ninevah. I’d never heard of her research and theories before and thought just the brief outline of them presented in the book was intriguing and made for a compelling case.