To build a solid foundation and score well in the UPSC Civil Services Examination (CSE), your booklist should be highly targeted. The rule of thumb for UPSC is “Read one book ten times, rather than ten books one time.”
Here is the definitive, highly recommended booklist for UPSC CSE, divided into foundational NCERTs and standard reference books.
UPSC CSE Prelims: Check Here
UPSC CSE Mains: Check Here