surely ou can get many answers on this but i can not ignore it on my thread because it is my experience from my fails which is forcing me to answer this question. The answer is straight NO. NO reference book is required for cbse 12 just straight away go for 12th biology NCERT book I have some steps to mug up each and every chapter of ncert. Obeying these steps will Surely get you 100 marks in boards
STEP 1: read chapter and understand it nicely, try not to learn only understand that chapter, underline( do not highlight it) main points(do not underline facts and examples provided in the book)
STEP 2: Now after finishing the chapter you are well aware of the content of the chapter now start learning it. Highlight(do not underline) facts provided in it like examples and else. Learn it twice or thrice or again and again untill you reach that satisfactory level.
STEP 3: In this step make short notes or facts sheet of that chater. Take a A4 size paper and in small writing note down all the important notes of that chapter for example note down all the headings,it’s example,meaning and else. Try not to exceed your notes more than a page. I have learnt whole ncert biology of class 12th and I believe that your notes will not exceed more than a A4 page. This is fact sheet i made for polymer chapter of chemistry i completed it in one page.