This extremely thin volume is a gem of a book, containing one of the most important revelations I've yet read about Japanese verb conjugation. Japanese Verbs and Essentials of Grammar identifies three components of each verb form: the stem, which never changes; the 5 bases, plus ta-form and te-form; and various endings which express the verb tense. For example, here are some bases and endings for kaku.

This is only a small example of the endings explained in the book. So far, we've learned only a few of these forms in class. We spent the first semester learning the 〜masu forms and the second semester learning ku and kanai. Then this semester, the new possible endings have been raining down on us furiously.

The problem is that our textbook is so focused on a conversational approach to Japanese that it does not do a good job of explaining the fundamentals of grammar that would make it easier to build a firm foundation, the foundation required to rapidly learn new grammatical forms. Every new grammar point is learned in isolation, disconnected from what's been learned before.

I first read this book about a year ago and it was the inspiration for the layout of my verb flashcards (stems with yellow backgrounds, bases in blue, endings in black). Now that we've actually covered all the bases, and are just learning new endings, I'm really, really thankful that I learned verbs this way. If you are struggling with Japanese verb conjugation, do yourself a big favor and pick up this book.