History can be a scoring optional subject for you if you have an interest in it. But still, I would suggest you read the blog uploaded on Rau’s IAs website named as- How to select Optional Subject for Civil Services Exam?
India’s Ancient Past by R.S. Sharma.
The Wonder that was India by A.L Basham for Ancient History.
Medieval India by Satish Chandra.
History of Modern India by Bipan Chandra.