As an English teacher, I use this book as my grammar bible. This book comes in two volumes: one for beginners and one for intermediate students. Each book covers over 100 grammar points. Each point gets two pages. On one page there is an excellent explanation of the grammar point along with examples. On the facing page, lots of grammar exercises are provided.
I don't use this as my classroom text since the activities don't lend themselves to communication. However, the communicative texts I do use either have poor or non-existant grammar explanations. When students have difficult questions about grammar, I often check with this book, since the explanations are quite clear and easy to understand. If students request some grammar practice homework, then I let them do the grammar activities as homework. It really helps students improve their accuracy.
I definitely recommend this to English teachers and students who are studying English. It would be a great reference book, and a good self-study supplement for students. If you can only afford one volume, I recommend the intermediate one because it answers some really diffult grammar questions well.