This is great little book for learning Japanese onomatopoeia (phew, glad the spelling checker is working!). Onomatopoeia (giongo/gitaigo) are words that sound like there meanings. English examples include "splash" and "click". They are used extensively in Japanese conversation, but they are not covered much in Japanese textbooks. This book is a great way to expand your vocabulary in this area.
Each chapter introduces five related onomatopoeia. A brief explanation of their meaning is given followed by a couple of example sentences. There is a manga-style illustration depicting one of the example sentences. At the end of each chapter there are some review exercises that test how well you remember the material.
I found this book very enjoyable to work through and helpful for learning onomatopoeia. It would have been nice to have English translations of the example sentences, but apart from that minor detraction, this is an excellent book.