Hello Sivakumar,

There are lots of books for lots of competitive exams and the books totally depends upon the exams which you want to give as from my side I will refer you some books for competitive exams or by subjects.

Defence exams- Arihant Pathfinder

For polity syllabus refer Laxmikant

For Maths Quantitative aptitude by R.S.Agrawal

For Science refer Ncerts

For English refer Wren an martin

For GK you have to read newspaper daily

Mostly be dependent on Ncerts from class 8-12

Hello,

For Quant Section, you can use RK Agarwal's Quantitative Aptitude/ M Tyra's Quicker Maths/Arihant's Fast Track Objective,

For Reasoning, MK Pandey's Analytical Reasoning or RK Agwarwal's Verbal and Non-Verbal Reasoning.

For English, the best grammar book is Wren and Martin, for vocabulary development Norman Lewis's Word Power Made Easy, for practice you can use Plinth to Paramouth or SP Bakshi's Objective General English.

For static portion of GK, you can use Lucent's GK, for dynamic portion read The Hindu on a daily basis, it'll also improve your English.