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
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