Hello.
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I can't say that ML khanna books are not useful nor they don't help help you. But, there are more good authors then ML.khanna for jee mains
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But it even varies from subject to subject

For chemistry,
R.C mukherjee for modern approach
Tandon for organic chemistry
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For physics,
HC Verma for vol 1&2
Walker for fundamentals of physics
DC panday for understanding physics
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For math's,
RD Sharma for objective maths
S.L loney for trigonomentry

And Many topics by different authors are suggested for best preparation.
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Here is the link which provides you which topic you should learn by different authors accordingly.

https://engineering.careers360.com/articles/best-books-for-jee-main
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Follow the provided link.This will help you out if every information and make you ready for examination to attempt with a confidence.
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Best of luck

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