Reference Books for UPPSC:

History:

1. New-NCERT, TN-Class:11/12, NIOS (Free)
2. History of Modern India - Bipan Chandra
3. Spectrum Modern History 
4. India's Struggle For Independence - Bipan Chandra 
5. India's Ancient Past - R.S. Sharma 
6. History of Medieval India - Satish Chandra

Geography:

1. NCERT (Class 6th to 12th)
2. Certificate Physical and Human Geography - Goh Cheng Leong 
3. Geography - A Comprehensive Study - Mahesh Kumar Barnwal 
4. Geography NCERT class VI to Class XII 
5. Oxford School Atlas – Oxford

Environment:

1. NIOS (Environment biodiversity) & NCERT
2. Science and Technology by Ravi Agrahari (Mcgraw-hill)
3. Last Six Chapters of 12th Class NCERT
4. India Year Book

Indian Polity:

1. Lakshmikant
2. Constitution of India
3. PRSIndia.org: latest Bills & Amendments

Economy:

1. Budget & Economic Survey
2. Indian Economy - Ramesh Singh
3. Uttar Pradesh Year Book
4. India Year Book

General Science

1. Lucent General Science
2. Science Subject NCERTs

Current Affairs:

1. Newspaper: Hindustan (Allahabad Edition)
2. Monthly Magazine  
3. 10Pointer Daily Current Affairs