Hello Purumandala

For BITSAT, just master this book: BITSAT Guide by Arihant. But before that, you need to build a good level by these things:

Physics: Start with HC Verma. Then go ahead with IIT JEE Questions directly. Dont go for any other crap books.Also other books from Arihant and GRB are good .. However if u have time left after doing previous years, you can solve Irodov, Resnick, Krotov etc !

Chemistry: NCERT most important. Other than that, for reference, use OP Tandon, MS Chouhan, Pradeeps, Morrison and Boyd, Himanshu Pandey, P Bahadur, SN Sanyal etc. Other books from GRB and Arihant are also good !

Maths: Start with NCERT, RD. Then go ahead with A Das Gupta, MCQ in Maths, Advanced Problems in JEE (Balaji) and then previous year questions from Arihant 39 years !etc More books of Arihant and GRB can be used if needed.

Practice previous year IIT JEE questions MANY TIMES (You can use Arihant 39 years for that  . Become perfect in them. Solve other people’s doubts. These will help you score better 

• Problem solving is important
• One should no only be good at problem solving but should be quick.
• Quickness dominates over accuracy in bitsat.
• You should know the shortcuts
• You be memorise as much as formulas for the exam.