Brother I personally like all these books because it contains such information which differentiates them from one another. If you have time then just have a bird’s eyeview of them and note down important points and facts & figures because these points, if written in paper, will help you in securing high marks.
2ndly for CSS IR paper you should thoroughly study the following books:
- International Relations by Prakash Chander
- Success in twentieth century world affairs by Jack Watson
- International Relations magazines (monthly or quarterly published)
This is my personal view you can also take help from other forum members in books selection.