which book is best for cbse math 12 chapter wise revision for 2021 exam
You can go with CBSE scanner books as published by different publishers like MTG, Arihant etc.
You should revise your text books and examples. If you can solve a lot of question papers (previous year/mock test) which will help you manage time.
Also you can prefer books by RS AGGARWAL and solve important problems from it.
I hope my answer helps. All the very best for your future endeavors!