Errorless (USS) is enough for maths for Jee main and BITSAT...
Yes, it is good book but other books are best like RD Sharma, SL Loney, I.A. Maron and Hall and Knight.
In order to score good marks in maths section in JEE Main and BITSAT lot of prctice is required. You should solve as many as MCQs for your practice. Solve previous year questions to know the level and you can solve timing test to work on your speed and accuracy.
Good luck!!
JEE Main 2025 College Predictor
Know your college admission chances in NITs, IIITs and CFTIs, many States/ Institutes based on your JEE Main rank by using JEE Main 2025 College Predictor.