Hello.

For mathematics

• Mathematics for NDA and NA

By R S Agarwal

• Pathfinder for NDA & NA Entrance Examination National Defence Academy/Naval Academy Conducted by UPSC.
• Objective General Knowlegde & Current Affairs (Level 2) : Useful for UPSC / State PCS / CSAT / Bank PO / NDA / CDS / MBA (English) by Disha Experts.
• Chapterwise-Sectionwise Solved Papers NDA & NA (Mathematics/English/General Ability) with Explanatory Solutions : Mathematics / English / General Ability with Explanatory Solutions Latest (English) by Arihant Experts

These are the books that you can prepare but don't get too confused what to study . What ever you study do it with a clarity.

Hope this is helpful.

Good luck.