Hello aspirant

There is no specific book for JNU entrance exam , you can refer previous year's papaers to know the level of questions. You should have basic knowledge of the subjects like history, Economics, international relations , philosophy, Indian politics.

You can refer the books given below

India after Gandhi - Ramchandra Guha

Indian Government and politics - A S Narang

International Relations in 21 century - pushpesh pant

Global politics by Andrew Heywood