"Rohel Phonetics: A Practical , Easy Approach with Magic Techniques a Unique book for Learners whose mother tongue is Bangla" Taken from the last flap of the book:

This book will help you transform your knowledge into your skill instantly. It is the ultimate help for acquiring a native or near-native pronunciation skill.

If you don't learn English as it is spoken by the native speakers, then what you are learning may not be English. So it is a good idea to train your tongue in the proper way. Well, just a minute ... We usually spend years for learning English. Now if you have to spend some more years for learning correct pronunciation, then maybe you will become old before you achieve your goal. But you need not worry now. This book will provide you with magic tactics, like many other books by this author; it will make your life easy and enriched.