Hello Aspirant,

It is very good thing that you have completed your JEE syllabus, so now it's time to practice as much questions as you can to make yourself confident and have a hands-on practice of questions. So I am enlisting down some best books for preparation of JEE-Main 2021 :-

@Physics

Concepts of Physics-H. C. Verma

Fundamentals of Physics-Halliday, Resnick and Walker

Problems in General Physics-I. E. Irodov

University Physics-Freedman and Young

Understanding JEE physics series-DC Pandey

Problem In Physics-SS Krotov

@Mathematics

Higher Algebra-Hall and Knight

Coordinate Geometry-S.L. Loney

Differential and Integral Calculus-N. Piskunov

Calculus and Analytic Geometry-Thomas and Finney

IIT Mathematics for JEE Main & Advanced-M.L. Khanna

Course in Mathematics for IIT-JEE-Tata McGraw Hill publication

Problems Plus in IIT Mathematics-A Das Gupta

Trigonometry-S L Loney

@Chemistry

Modern Approach to Chemical Calculations-RC Mukherjee

Organic Chemistry-Solomons and Fryhle

Concise Inorganic-J. D. Lee

Organic Chemistry-Morrison and Boyd

University Chemistry-Freedman and Young

Physical Chemistry-N Awasthi

Arihant's Practice Book Chemistry for JEE Main And Advanced-R.K Gupta

For complete details kindly check out the link given below :-

https://engineering.careers360.com/articles/jee-main-preparation-tips-for-january-exam

You can also check out the JEE-Main knockout package for preparation of JEE-Main 2021 from the link given below :-

https://learn.careers360.com/knockout-jee-main-april/?product=27&icn=knockout-jee-main-2021-january&ici=

I hope this information helps you.

Good Luck!!