Which is the best textbook (English language) to study about the Indian government and political system?

Yes, even I would recommend you sample papers by APC Books. They have questions based on updated syllabus and pattern which helps you to understand better and score well.

Below mentioned are some of the finest books: 1. Indian Polity for Civil Services Examinations: M. Laxmikanth is a really useful book for all stages of examinations. 2. Introduction to the Constitution of India - Durga Das Basu. A much more authoritative text on Indian polity. 3. Good reference