Hello there,
These are good books but these maybe not enough for BITSAT 2021. I'm suggesting you few more books, try preparing from these books as well.

For Physics:
1. Concepts of Physics (H.C.Verma)
2. Problems in General Physics (I.E.Irodov)
3. Arihant Physics (D.C.Pandey)

For Chemistry:
1. Organic Chemistry (M.S.Chauhan)
2. Inorganic Chemistry (O.P. Tandon)
3. Physical Chemistry (N.Awasthi)

For Mathematics:
1. Differential Calculus (Arihant)

The books you mentioned are good but not enough. Also, solve the previous year question papers. They help a lot!

Hope this answer helps you.
Good luck!!

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