Hi! 

There are some books available in the market for JNU B.A. Hons . I can't say about best. But make sure they are the updated version. I will suggest you the following:

Previous year JNU papers

Arihant Model paper for BA JNU Entrace

Manorma Year book( not cover to cover, for reference only)

JNU model paper. it will be on Jnu website.

brush up your English grammar and practice some essay writing

Read current affairs

Hope it will help you:)