Hello Imtiyaz ,

The following are the best books according to me for the exam.

1. Rajani Kothari: Politics in India
   
2. Nirja Gopal Jayal and Pratap B. Mehta: Oxford Companion to Politics in India
3. Paul Brass: The Politics in India since Independence
4. Indian Polity: M. Laxmikant
5. Working in a Democratic Constitution: A History of the Indian Experience: G. Austin

Hope this helps.

Regards

Tanushree Seth