Dear student,

Ncert books is one of the easiest and basic books that every student must read if they are finding some concepts difficult to understand from their own.
Now, there are different ncert books for different standards, for eg - class 12th ncert book is separate and class 11th ncert book is separate. So, it's not a combined book for every standards. It's divided for ever standard so, that students can prepare accordingly to their respective standards and they don't take load or burden of any kind. Also there are different ncert books for different subjects.
There is no combined ncert book. For physics it is different. For chemistry it is different. For other subjects too, the ncert book is different, and these books are made as per standards.