It is a really good book for you study English. In this book you can study how to speak English and many grammatical points of English language which are very important. This book is more than 40 mb, so it may take you a little long time to download. And the book is also designed for self-study. You can learn by yourself without any teachers to guide you because the book will be a teacher for you.
It is one of the best book can actually have to improve your English skills and earn reputation in your life. To have a ability to speak any foreign language is not easy and it is an advantage for you in many things such as applying for a job or a government position.