98% of the questions come from NCERT books. And for the remaining 2%, there are books that you can study from different publishers. If you want to appear for NEET 2021, you can prepare with the help of our NEET Knockout package: https://learn.careers360.com/knockout-neet-may/ . Few books that we can recommend for your NEET preparation are:

Physics:

NCERT Physics Class XI & Class XII
Concepts of Physics by H. C. Verma
Objective Physics By DC Pandey
Fundamentals of Physics by Halliday, Resnick and Walker
Fundamental Physics by Pradeep
Problems in General Physics by IE Irodov

Chemistry Best Books:

NCERT Chemistry textbooks for Class XI and XII
Physical Chemistry by OP Tandon
ABC of Chemistry for Classes 11 and 12 by Modern
Concise Inorganic Chemistry by JD Lee
Dinesh Chemistry Guide
Practise books by VK Jaiswal, MS Chauhan and N Awasthi

Biology Best Books:

NCERT Biology Class XI and Class XII textbooks
Biology Vol 1 and Vol 2 by Trueman
Objective Biology by Dinesh
Objective Botany by Ansari
Pradeep Guide on Biology
GR Bathla publications for Biology

Dear aspirant

As if we talk about NEET 2020 then almost all 180 questions were from NCERT Book of PCB only there was no any questions which was out of syallbus.  As NTA is conducting exam so most of the question are from NCERT Books only. There might 2-3 questions which may come out of syallbus they will mostly from current affairs or general knowledge. You may take help from this article which link is given below

https://www.google.com/amp/s/medicine.careers360.com/articles/neet-preparation-tips/amp

Hope it helps