To crack the JEE main exam, a good knowledge of concepts and fundamentals is necessary. NCERT books will help you to clear your basics and concepts. If you go through with the NCERT books line by line then it will be sufficient to understand the basic and you can score around 250 but its depends on your efficiency.

So i would like to suggest you, for practicing questions and better understanding of the some concepts you can also try other publishers books.

For Chemistry you can refer:

• Inorganic Chemistry by OP Tandon
• Organic Chemistry by Dr. AK Virmani
• Physical Chemistry by Dr. P Bahadur

For Physics you can refer:

• The concept of Physics Vol. 1 and 2 by HC Verma
• Fundamentals of Physics by Halliday, Resnick, and Walker
• University Physics by Freedman and Young.

For Mathematics you can refer:

• Higher Algebra by Hall and Knight
• Calculus and Analytic Geometry by Thomas and Finney, etc.
• you can follow a books “Arihant publication” these are more sufficient to crack the JEE Mains Mathematics.

Yes you need some extra books for solving practice problems that is setting your hand for MCQs. Ncert is good enough to clear your concepts, but to build them stronger and to boost your confidence, you need some very proper mcq books. I'll try to guide them... For physics you can use either of DC PANDEY, IRODOV or HC VERMA. For chemistry do use either of ABC OF CHEMISTRY, GRB or ARIHANT. For Maths you can refer to RD Sharma.

Best wishes. Thank you.