This book is no longer published.
For other books by Ash Chakraborty, view Ash Chakraborty's Smashwords author profile page. It's possible you may find a newer edition of this book there. Alternatively, if you don't find another version, the author profile page may provides links to the author's web site and social media. You could try contacting the author there and ask them to return the book to Smashwords.