Which NCERT books should I read first for UPSC and in what sequence?

To build a strong foundation for the UPSC Civil Services Examination, you should prioritize Geography, History, Political Science, and Economics NCERTs. 

1. Recommended Books and Sequence
Geography (Context for all subjects):
Classes 6–10: For basic concepts on climate and resources.
Class 11: Fundamentals of Physical Geography

History (Chronological timeline):
Classes 6–10: Simple overview of events.
Classes 11–12 (New): Themes in Indian History
Old NCERTs (Highly Recommended): R.S. Sharma (Ancient), Satish Chandra (Medieval), and Bipan Chandra

Political Science (Understanding the system):
Classes 9–10: Democratic Politics I & II.
Class 11: Indian Constitution at Work is the most critical for Polity fundamentals.

Economics (Core vocabulary):
Classes 9–10: Basic definitions.
Class 11: Indian Economic Development
Class 12: Introductory Macroeconomics

2. Effective Reading Strategy
Begin with a "story-mode" read to grasp the big picture. On your second pass, highlight key terms and explicitly link chapters to the UPSC syllabus Finally, limit your detailed note-making to Classes 11 and 12, as these cover lower-class concepts more comprehensively.