Amazing!! This book is great! It's full of useful snippets of information on the cultural details you may have noticed (or missed, shame on you) in anime (and to a lesser extent manga). Alphabetically ordered, each object, place, person, or other piece of trivia has it's own succinct little paragraph; this makes the book great for looking up the thing you want in seconds; or for just dipping into at random. Which you will!
Some of the things explained in this book will greatly help you understand your anime to the full; others are in there just for fun. Some will have you scratching your head in disbelief. For example, the Kappa: In Japanese mythology, a tortoise-like spirit who has a hole in it's head for storing water, and is fond of cucumbers..!?!? Who makes this stuff up? The Japanese, apparently!
So, to sum up, essential for any anime fan (and even people who don't think they like anime should read this). A fascinating insight into a unique culture; in the context of anime/manga... does learning about other countries get better than this? I think not! Get it now, and amaze your friends with your worldly knowledge and trivia! If only it was longer!