Hello Aspirant,
There is no any particular book for the preparation of the exam, you can prefer the Graduation level books to cover the Entrance syllabus. You can download the previous year papers of JNU with the given below link.
http://admissions.jnu.ac.in/searchquestionpaper.aspx
You can also check the exam syllabus with the given below link.
https://jnu.ac.in/admission/e-prospectus-2019-20.pdf
Good Luck!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile