Despite its small size, this book covers topics glossed over by supposedly more complete references. For example, plenty of colloquial and informal verb forms are covered, and the last chapter is a reference of various idiomatic expression that take a verb base.
The book does have some downsides, though. Most of it is structured in a way more fitting for a guide than a reference. It takes the typical constructive approach of building verb forms starting with the base, useful for composing Japanese text, but less useful to a beginning student who would probably be more interested in reading, and would benefit from a deconstructive approach. Japanese text is presented in romanized and kanji forms, which isn't bad at all, but I would have preferred kanji with furigana only. And finally, the typography is a bit too busy, and the small, information-rich pages can be rather hard for your eyes.
Nevertheless, this book can greatly improve your understanding of Japanese, and I wouldn't hesitate to recommend it to any beginning and intermediate student!