Hi

Top books which you can follow for UPSC examination preparation are listed below subject wise:-

HISTORY

*NCERT XI (Ancient & Medieval)
*NCERT XII (Modern Indian History)
*Facets of Indian Culture Spectrum
*From Plassey to Partition - A History of Modern India

Indian Art & Culture

*Indian Art & Culture - Nitin Singhania

Polity

*NCERT IX-XII
*Indian Polity M Laxmikanth

Geography

*NCERT VI X (Old Syllabus)
*NCERT XI, XII (New Syllabus)
*Certificate Physical Geography G C Leong
World Atlas

Economics

NCERT XI
*The Indian Economy Sanjiv Verma
*Indian Economy by Ramesh Singh
*Economic Development & Policies in India Jain & Ohri

Environment

*Class XII Biology (last 5 chapters)
*Environment by Shankar IAS Academy

International Relations

*NCERT XII (Contemporary World Politics)
*Current Affairs ( read newspaper )

To get the complete list of books go through
https://competition.careers360.com/articles/books-for-upsc-ias

Also,

As you are preparing for your UPSC civil services examination just after your 12th you must be pursuing your graduation right now as to be eligible for UPSC one needs to be at least a graduate so make a routine or a time table and try to maintain a balance between your studies for  graduation and your studies for UPSC preparation and religiously follow it , take short breaks in between your studies.

*Read newspaper daily and keep yourself updated with the current affairs

*Choose your optional subject wisely , choose the subject you have interest in.

*Make short notes for each subject, it  will help you in your revisions a lot as syllabus is wide

*Revise :- there's no point of preparing for the exam if you couldn't recall anything in the UPSC Examination so you should stress on revision as well.

*Solve previous year question papers and mock test papers ;- You should solve these , it will give you idea of types of questions asked and their difficulty level and will help you a lot.

*Also work on your communication skills and personality development as it plays an important role in your interview round

For more tips go through

https://competition.careers360.com/articles/how-prepare-for-upsc-ias

If you have any other doubt then feel free to ask them :) we are always here to help you out and guide you

Thankyou