As an English teacher, this book is a great way to introduce grammar into the lesson with little planning, especially in a one-to-one situation. It is also good for setting homework to consolidate the grammar covered in lessons. The methodology is sound and it focuses on simple explanations with plenty of practice. It also has great "revise the basics" sections that really keeps the explanation to a minimum and focuses on getting the studying to use the target language and 'discover' the pattern for themselves. It also avoids unrealistic examples/exercises and tries to focus on things that a student may actually need the language for. The section on spoken grammar is also quite interesting as it looks at things often not covered in textbooks.
For the student, this is a great way to develop your grammar. I would recommend this as a good reference book to supplement an English course if you feel as though you're not totally confident with some aspects of grammar. I wouldn't recommend working through this book from start to finish, rather visiting certain sections for practice.