Dear Rohit,

UPSC Civil Services Prelims will have two papers.

The Paper 1 will be General Studies I (GS I) comprising many sections including Economics, Geography, Political Science, and Science, and the Paper 2 is known as General Studies II (GS II) which will test the aptitude of UPSC IAS aspirants for Civil Services examination.

The GS II paper is alos called as CSAT (Civil Services Aptitude Test).

Best books to prepare for your exam is NCERT books.

Apart, from NCERT you can refer below recommended books

- Indian Polity for Civil Services Examinations by M. Laxmikanth (Polity)

- Indian Art and Culture by Nitin Singhania. (Culture)

- Indian Economy by Ramesh Singh. (Economy)

- Economic Survey by Ministry of Finance. (Economy)

- India Year Book (Current Affairs)

- A Brief History of Modern India by Rajiv Ahir (Modern India)

- General Studies Paper 2 Manual by MHE (CSAT)

Good luck!!