Hello dear student,

If the word that is NIOS board have provided you with some specific or different books than CBSE books of 11th and 12th then according to my opinion we should go for those books and by them the syllabus don't be much different as NIOS is also a recognised board and equivalent board to CBSE. Sudesh no need to worry about it. While to appear in the exams of NIOS that is board exams you should buy NIOS books when we can prepare for neet considering NCERT books for CBSE books. Books for NIOSand CBSE are same then there is no problem.

Best wishes