Move from basics to classics! 

Hi,

Since you are in 11th standard, you have ample time to prepare for BITSAT. Start by studying the basics, practising and then giving mocks. 

First read and solve NCERT books of all subjects. Then for Physics, solve 'Concepts of Physics by H. C Verma Vol 1 and Vol 2'. For Chemistry, read 'Physical Chemistry by N Awasthi', 'Organic Chemistry by M.S. Chauhan', 'Inorganic Chemistry by O.P.Tandon' and for Mathematics, use Class 'XI & XII by R.D. Sharma'. For English and Logical Reasoning, solving past year questions would be enough but you can obviously read 'Wren and Martin'. 

You can also buy 'The Pearson Complete Guide to the BITSAT (English) by One Learn Education' to get all subjects in one book along with a few mocks. Besides, buy BITSAT mocks and practise.

For more details, check: https://engineering.careers360.com/articles/bitsat-2019.

Hope this helps.

Cheers!