Here are some of the books you can prefer:

• History of Modern India - by Bipin Chandra (History)
• India's Struggle For Independence - by Bipin Chandra (History)
• Indian Economy, NCERT std. 12th economics course book
• Geography Of India - by Majid Husain (Geography)
• Verbal and Non-verbal Reasoning - by R.S. Aggarwal
• Economic Survey
• Indian Polity - by M. Laxmikant (Political Science)
• Indian Art And Culture - by Nitin Singhania (culture)

Good Luck!

Paper I - General Studies
1.    History (Indian History and Indian National Movement)
NCERT books IX, X, XI, XII
Modern India by Bipin Chandra

2.    Geography (Indian and World Geography)
NCERT books IX, X, XI, XI
General Principals of World Geography by Charles Farro
School Atlas

3.    Economics (Indian Economics and Economic Theory)
 An Evolution of Indian Economy by I.C. Dhingra
Economic Survey of India by Govt. of India
Economic Dictionary by Penguin                 

4.    Polity (Indian Constitution)
An Introduction to the Constitution of India by D.D. Basu

5.    General Science (Physics, Chemistry, Biology)
NCERT books IX, X

6.    Environment (Ecology, Bio-diversity, Climate Change)Biology and Geography NCERT Books plus current events on Environmental Issues

7.    Current Affairs
Hindu and Economic Times Newspapers
Frontline, Political & Economic Weeks Periodical

Paper II – Aptitude
1.    Numeracy-NCERT Mathematics VII, IX, X
2.    Data Interpretation-Data Interpretation and Data Sufficiency by Tyra and Kundan
3.   English Comprehension and Communication-Objective General English by R.S. Agarwal

4.    Logical Reasoning-A Modern Approach to Verbal Reasoning by R.S. Agarwal