B.Sc

Hi,
At B.Sc level, one doesn't follow a single textbook like 12th class's maths NCERT book (I'm not counting the reference books because as far as I know CBSE doesn't mention them explicitly in the list of books to be followed during 12th). If you are doing mathematics (H) from a Delhi University college then in your first semester you will be having at least 4 subjects and for each subject there will be at least 23 books you will be asked to follow. But from each book either few sections of a particular chapter or at max. 1/2 chapters are to be covered. So don't worry about the number of books to be followed. The details like name of subjects particular semester, name of the books to be followed, etc. can be found in the syllabus of B.Sc (H) mathematics and this syllabus is available on the official website of Delhi University.
As far as semester exams are concerned mostly the textbook questions are asked in the semester exams. You don't have to prepare for the exams from reference books like we do in 12th class. Go through previous year's paper, you'll know which topics require more attention and one can cover the whole syllabus easily if starts studying regularly one month before the semester exams but be consistent and please do read from books not from the notes of any coaching institute because reading from the books helps a lot afterwards. Do listen to the teachers you find worth listening during lectures, it helps.