Borad, these are a list of some  books which you should refer for preparation of BITSAT Examination, but keep in mind these are not the only sources where you can get the preparation material as there are many other good reference materials too :---

* NCERT Textbooks which are most important and necessary to be completed in order to improve the basics of all the topics

* RD SHARMA for MATHEMATICS

* ARIHANT TEXTBOOKS for MATHS

* OP TANDON for CHEMISTRY

* HC VERMA PHYSICS

* CENGAGE for MATHS

* ARIHANT PREP GUIDE TO BITSAT

* FUNDAMENTALS OF PHYSICS ( HALLIDAY, RESNICK, WALKER)

Hope this helps you in preparing well for the exam and increase your chances of getting your desired college and courses.