Firstly which you need to do is to skim through the syllabus ..If u will see the syllabus then it consists of Culture, Indian History and Indian National Movements.
Starting with NCERTs is the most accepted approach towards any subject for IAS Exam preparation because they will provide the foundation of your further advance books then, here are some books which will cover almost all the part of the syllabus.
For Indian culture-
Go through ‘Indian art and culture by Nitin Singhania‘.
For the purpose of convenience and ease, Indian history has been divided into three parts
1. Ancient history
2. Medieval history
3. India after 1857.
For ancient Indian history –
Study ‘India’s Ancient Past’ by R.S. Sharma which will help you stronger in Ancient and cultural history part.
For medieval history of India
History of Medieval India by Satish Chandra will suffice the requirement. Only a few questions normally asked in the UPSC exam although it is important.
For the history of Modern India
Read ‘History of Modern India‘ by Bipan Chandra
For Indian national movements
India’s struggle for independence by Bipan Chandra which is a very good book for the modern part. This book a little bit fatty and time consuming but it will give you broad knowledge about the topic. This book can read like a novel, explains holistically each and every happening of the freedom struggle period. History of Modern India by Bipan Chandra also serves the purpose of the exam. Almost the same contents are laid out in both of these books but a little bit different is there. Check the full list of IAS Books useful for Prelims and Mains. If you are Hindi medium aspirant Check this link
If one who has facing time constraints, they can read A Brief history of Modern India by Spectrum Publication which is almost a summary of India’s Struggle for Independence.
I hope this would help you to simplify your preparation for Indian History!