Greetings !

As there are lot's of books and sources available in market for UPSC preparation, most of the students end up in buying 2-3 books of single subject and finally find difficult to complete the portions. So i would recommend you to stick on to one single best source for information, revise it several times. Some of the books are follows, you may visit unacademy, Byjus IAS for more details . If any doubts, pls feel free to ask. Wish You All the Best !!

SUBJECT	BOOKS
History	India’s Struggle for Independence – Bipan Chandra Facets of Indian Culture – Spectrum NCERT XI (Ancient & Medieval) NCERT XII (Modern Indian History)
Geography	Certificate Physical Geography – G C Leong NCERT VI – X (Old Syllabus) NCERT XI, XII (New Syllabus) World Atlas
Indian Polity	Indian Polity – M Laxmikanth NCERT IX-XII
Economics	Indian Economy by Ramesh Singh Economic Development & Policies in India – Jain & Ohri NCERT XI
International Relations	NCERT XII (Contemporary World Politics) Current Affairs
CSAT	Tata McGraw Hill CSAT Manual CSAT II – Arihant Verbal & Non-Verbal Reasoning – R S Aggarwal

Dear Ajeet,
I would like to tell you that there many good books available in the market for UPSC Examination.
You can refer to NCERT books for subjects like history, geography, Indian polity, economics and international relations.
Apart from NCERT you can use Indias Struggle for Independence by Bipan Chandra for history.
Also books by Indian authors will help you in UPSC Examination.

I hope this information helps you.
All the best