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.
Books are still one of the most effective methods of learning source until today even though technology is changing how people access educational resources is changing quickly. But the way how a book is published has been changed already and people have already adapted to these changes without any delay since it makes them access the resources easily and cost effectively.
The main reason why people use ebook rather than a paper printed book is because the ebook has ease of use, better mobility and user friendliness. As mobile devices are the main tool to access resources, educational methods is also needed to follow these changes.