Hello Aspirant.

You currently have a lot of time to prepare well for your JAM examination. Some of the books best for this examination are.

1. Integral Calculus by F. Ayres

2. Linear algebra by Seymour Lipschitz

3. Real Analysis by HL Roden

You can also buy for revision mathematics book by Arihant publication. It'll help you a lot.

Best of luck !