As surveys of the history of geopolitical thought go, this is one of the most robust and well-edited I have seen.
A range of intellects from the ancient world to the modern day are presented, and while unique issues arise that differ between eras - several "through-plots" or universal themes that recur again and again provide a great overview of the both the complexity of the modern world and the oft-understated complexity of the old one.
A great resource to consult from time to time, after the initial read. Have your highlighters ready!