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.
This is a book in which you can learn how to be a good writer without having an instructor. Is it not cool? Well, it is cool for those of people who do not have time to study writing course and just prefer an individual study to other ways of learning methods. As said before, this book is a great place to start learning, by yourself how to write professionally.