Hello,

Go through the study materials of IGNOU, that's more than enough, you don't have to read any other books if you're thorough with the syllabus of your course by going through IGNOU books, the study materials are written in lucid and easy to understand language, and go through previous year papers at https://webservices.ignou.ac.in/Pre-Question/, this will help you in knowing marking scheme, important topics etc, accordingly you can plan which topics to give more importance, and which to skip, if you have time you can also make notes, this is quite useful for revision during the exam time, if you go through previous year question papers then you can see which questions are being asked quite often, and prepare for the same, this helps you a lot in scoring good marks.