Hello Aspirant,

See NCERT books are must to read books so I am enlisting down some best side books for preparation of JEE-Advance 2021 and note that these are apart from NCERT, you have to read concepts through NCERT and then you can solve questions of different difficulty levels from these side books using the same concept that you read from NCERT so that your concept will built in your mind forever :-

@Physics

Concepts of Physics by H C Verma (Vol-1 and Vol-2)

Fundamentals of Physics by David Halliday/Resnick/Walker

IIT JEE Physics by Arihant (35 years Chapterwise Solved Papers 2013-1979)

@Mathematics

Objective Mathematics By R.D. Sharma

Plane Trigonometry and Coordinate Geometry (Two Books) by S.L Loney

Problems in Calculus Of One Variable by I.A.Maron

Integral Calculus for IIT-JEE by Amit M Agarwal (Arihant Publications)

A Text Book of Algebra For JEE Main & Advanced by Dr. SK Goyal (Arihant Publications)

@Chemistry

Physical Chemistry by OP Tandon

Modern Approach to Chemical Calculations by R.C. Mukherjee

Organic Chemistry by O.P. Tandon

Organic Chemistry by Paula Bruice Yurkanis

Organic Chemistry by Morrison & Boyd

Inorganic Chemistry by J.D Lee

Inorganic Chemistry by O P Tandon

If you are preparing for JEE-Advance then you can check out the link given below for best preparation tips :-

https://engineering.careers360.com/articles/jee-advanced-preparation-tips-physics-chemistry-and-mathematics

You can also check out the complete JEE-Advance 2021 syllabus from the link given below :-

https://engineering.careers360.com/articles/jee-advanced-syllabus

I hope this information helps you.

Good Luck!!