In the UPSC mains exam, a candidate has to be Choosy about the books. No one have to read all the list of these books. Our Experience says, you only have to read 1 reference book. Alongwith this, you need to have full command on news articles. Try to use the GOOGLE BABA as much as you can for a topic.
To understand the UPSC exam, one needs to understand the IAS syllabus. This helps to eliminate wasteful efforts like reading unnecessary topics leading to a loss of time and keeps one strictly aligned to the expectations of the UPSC from day one.
UPSC 2021 syllabus [UPSC Civil Services Prelims and Mains] has been released, along with the official notification for the Civil Service Exam on 4th March 2021.