Theories of International Politics and Zombies is Daniel Drezner’s mostly tongue-in-cheek* discussion of various theories’ takes on the zombie threat.
Having watched two zombie shows in my life — The Omega Man** when I was 11, and The Walking Dead this year — I consider myself expertly qualified to comment on Drezner’s book: It is fun.
So: What do the major theories of international politics think about the zombie apocalypse?
Realism and realpolitik: According to Realists, the international world is one of anarchy — there’s no overarching world government, so each state can do what it wants. Consequently, “in a world of anarchy, the only currency is power,” and “the anarchic global structure makes impossible for governments to fully trust each other, forcing all states to be guided solely by their own national interests.” 
The zombie threat? Not a lot would change internationally, according to Realists. As with earlier disasters and plagues in history, those nations powerful enough to deal with the threat would do so, using any methods at their disposal; some weaker nations might succumb or be absorbed; and after the zombies are contained or eliminated, the long-term global trend of the pursuit of national interests would continue as before.
Liberalism and international cooperation: Liberals believe our prospects for win-win global institutions are strong and so they push for “a world of economic interdependence, democratic governments, and international institutions [that will] foster extensive amounts of multilateral cooperation.” 
As for zombies, the liberal system might seem weak — its openness giving zombies more opportunities to spread around the globe — but at the same time the robustness of the liberal world would enable it more easily to marshal resources and coordinate responses across borders to handle the threat.
(Of course, Drezner notes, a liberal world would likely also spawn organizations devoted to zombies’ rights and welfare.)
Plus there are additional chapters on Neoconservatism and the Axis of Evil Dead, the Social Construction of Zombies, the challenges of semi-functional Bureaucratic Politics — turf wars, cover-your-ass incentives, and general government incompetence 
(imagine FEMA in charge of the Zombie Response Team), and more.
Drezner gives us much to chew on in this lean volume. He compactly summarizes a large bodies of theory into digestible chapters. And unless one is brain-dead, etc.
Notes:
*Tongue-in-cheek: Drezner’s own tongue in his own cheek, not a zombie’s.
**I’m open to debate whether the plague-surviving mutant humans in The Omega Man were, technically, zombies. I know it’s a sensitive topic.