I would suggest that you should try to study for a week or so and then decide. I believe reading scholastic articles and keeping up on the news from various different publishers is the best way to stay informed on International Affairs. The theory is perhaps the bulk of the foundational works along with International political economy (IPE) and International organizations/Law. Then there are a lot of dynamic parts; what is happening around the globe etc.
I would suggest you read global politics by Andrew Heywood as a starter and then decide whether you find it interesting or not. I hope that helped a bit.