Dear Ambuj,

For BITSAT you can go for Arihant book as it has many questions based on BITSAT syllabus which are very important for your practice. 

It is also good book to clear your concepts. 

Make sure you complete your NCERT first as it will help you to prepare for your exam better.

Solve previous year papers as well to understand the exam pattern and to know to the level of the exam.

Practice mock test series as much as you can as it will help you to build your speed which is important to carck BITSAT exam.

If you are well prepared for JEE Main you can easily crack BITSAT exam.

All the Best!!