World Politics , written by Charles Kegley, is one of the best books for this subject. Relying on one book or source can be detrimental. I would like to suggest you another book that can help you in this regard i.e. "How the world works", written by Russel Bova.
First read a topic from Bova's book and then read the same from Kegley's book.
This will help you in grasping the concepts. Moreover, where you find it difficult to understand a topic from aforementioned sources, then internet can be helpful.

Strategy:
Start with the Introduction and Theories as mentioned in the syllabus. Also give a read to Balance of Power, Deterrence, Nationalism, Internationalism, Globalization, Fascism, Democracy, Socialism, Communism, Capitalism. This will help you in understanding the core concepts of this subject.