For the UPSC Mains exam, a thorough understanding of the syllabus and in-depth study of various subjects are crucial. Here’s a list of recommended books for each paper:

General Studies Paper-I: Indian Heritage and Culture, History, and Geography

1. Indian Culture
   • “Indian Art and Culture” by Nitin Singhania
2. Modern Indian History
   • “India’s Struggle for Independence” by Bipan Chandra
   • “Modern India” by Bipan Chandra
3. Ancient and Medieval India
   • “Ancient India” by R.S. Sharma
   • “Medieval India” by Satish Chandra
4. Geography
   • “Physical Geography” by Savindra Singh
   • “Indian Geography” by Majid Husain
   • “Certificate Physical and Human Geography” by G.C. Leong

General Studies Paper-II: Governance, Constitution, Polity, Social Justice, and International Relations

1. Indian Polity
   • “Indian Polity” by M. Laxmikanth
   • “Introduction to the Constitution of India” by D.D. Basu
2. Governance and Social Justice
   • “Governance in India” by M. Laxmikanth
   • “Social Justice and Empowerment” by S.P. Verma
3. International Relations
   • “International Relations” by Pavneet Singh
   • “The India Year Book” (for current updates on international relations)

General Studies Paper-III: Technology, Economic Development, Bio-Diversity, Environment, Security, and Disaster Management

1. Economics
   • “Indian Economy” by Ramesh Singh
   • “Economic Survey” (Annual publication by the Government of India)
   • “Budget” (Annual publication)
2. Environment and Ecology
   • “Shankar IAS Environment” by Shankar IAS Academy
   • “Environment and Ecology” by Majid Husain
3. Security and Disaster Management
   • “Security and Disaster Management” by M. Laxmikanth
   • “Disaster Management” by R.B. Singh

General Studies Paper-IV: Ethics, Integrity, and Aptitude

1. Ethics
   • “Ethics, Integrity, and Aptitude” by M. Laxmikanth
   • “Ethics in Governance” by K. S. Sharma
2. Case Studies
   • “Case Studies in Ethics, Integrity, and Aptitude” by S. S. Rao

Optional Subjects

The choice of books will depend on your selected optional subject. Ensure you use standard reference books and previous years’ question papers for your specific subject.

General Resources

1. Previous Years’ Papers
   • “UPSC Civil Services Mains Previous Years’ Papers”
2. Current Affairs
   • “The Hindu” or “The Indian Express”
   • Monthly current affairs magazines
3. Essays
   • “Essays for Civil Services” by R. C. Agarwal

These books provide a comprehensive foundation for each subject and are highly recommended for detailed and structured preparation.