Sure! Here are some recommended books and a step-by-step guide to help you get started with your UPSC preparation:

1. Understanding the UPSC Exam:
Before diving into the books, it is important to familiarize yourself with the UPSC exam pattern, syllabus, and requirements. You can refer to the official UPSC website or reliable sources like EduRev for detailed information.

2. Basic Books for Reference:
- History: "India's Struggle for Independence" by Bipin Chandra, "History of Modern India" by Spectrum
- Geography: "Certificate Physical and Human Geography" by G.C. Leong, "Oxford School Atlas" by Oxford University Press
- Polity: "Indian Polity" by M. Laxmikanth
- Economy: "Indian Economy" by Ramesh Singh
- Environment: "Environment for Civil Services Prelims and Mains" by D.R. Khullar, "Environment and Ecology" by Majid Husain
- Current Affairs: Newspapers like The Hindu or Indian Express, and monthly magazines like Yojana and Kurukshetra

3. NCERT Books:
NCERT books are highly recommended for building a strong foundation in various subjects. You can start with the following NCERT books:
- History: Class 6 to 12
- Geography: Class 6 to 12
- Polity: Class 6 to 12
- Economy: Class 9 to 12
- Science: Class 6 to 10

4. Optional Subject Books:
If you have chosen an optional subject for your UPSC exam, refer to the recommended books specifically for that subject. You can find subject-wise book lists on the EduRev website.

5. Newspapers and Current Affairs:
Stay updated with current affairs by reading newspapers daily. The Hindu and Indian Express are popular choices. Make notes of important news, events, and government schemes for future reference.

6. Mock Tests and Previous Year Question Papers:
Practice mock tests and solve previous year question papers to familiarize yourself with the exam pattern and improve time management skills. Analyze your performance and identify areas that need improvement.

7. Online Study Materials and Resources:
Along with books, utilize online study materials, video lectures, and resources available on platforms like EduRev. They offer comprehensive study material, notes, and practice questions for UPSC preparation.

Remember, while books are important, it is equally essential to develop a proper study schedule, revise regularly, and stay focused. Stay motivated, seek guidance from experienced mentors, and make use of all available resources to achieve success in the UPSC exam. Good luck with your preparation!

Start with NCERTs of class 11th 12th polity, history,geography and economics.(if u have time read social science and science book of 9th and 10th Ncert)

if u are joining any coaching,they will provide u with all material but if u are preparing yourself there are standard books for every subject.I would recommend you to go with a single standard book for every subject rather than running for many books only for 1 subject.
so for ancient history: u can go with rupinder singh or R.S sharma
medieval history: satish chandra
modern : bipin chandra (india's struggle for independence)
polity : Laxmikant
geography: cheng leong
economics: Ramesh singh
for International relations, ethics ,society and internal security go with vajiram and ravi notes and then if required move for standard book.
This is all I want to say.Also I might have missed something, sorry for that.
and yes these books I am using myself that's why recommended you otherwise you are free to go with your choice anyway.
All the best !