Assuming that I'm answering this to an absolute beginner.
To begin with… you should have a hardcopy of syllabus. Give yourself some 15–20 days or atleast a month to understand the demand of the exam.
After learning syllabus you will get the basic idea of what subjects this exam is all about. I mean the sub you hv to focus upon. Develop the habit of reading newspaper 📰 be it Hindu or Indian express.
Now, comes the role of book in the picture. NCERTs for now. It is advisable to read 6--12 NCERTs of social science. But it may varies person to person. Some start with 9 or even with class 11th without having any issues in understanding.
As soon as you complete NCERTs, jump on to standard books like Laxmikanth, spectrum etc.
There are no bad or best books as such. So I would pen down the books which remains common for each aspirant.
Ancient-- RS sharma/ Tamil Nadu board class 11th
Medieval-- Satish chandra/ “”””””””
Modern-- Spectrum or Bipan chandra, either of them.
World history-- 9th and 10th social science ncerts or Arjun dev.
Art and culture-
Class 11 Fine arts NCERT
11th and 12th NCERTs+ GC leong(selectively).
11th and 12th NCERTs
NCERT of 11 and 12th + Laxmikanth
Ncert class 11th
Class 12th Macroeconomics ncert.
Shankar IAS book.
Science and technology-
Newspaper and magazines.
Don't restrict yourself to just one booklist. Search toppers blogs, go through their talks on YouTube. And conclude your booklist accordingly.