Mark Blitz's (old prof of mine) Plato's Political Philosophy is more straightforward, less ambitious, probably more correct because "safer." I feel like I understand this book because I heard it all from Blitz's mouth already and I read his earlier book on the Statesman. This only covers Statesman/Republic/Laws, well trod ground by Leo Strauss. Still, it's excellent. Highly recommended.
Execellence Unleashed by Paul Rasmussen (never heard of him until now) is the first book length look at Machiavelli and Xenophon, my two favorite writers. Frankly, this pisses me off in that I could have written this book. Much of what he writes I in fact have written in papers for the APSA and in one published article. But I never pursued it all. He has done a very good job so no complaints, except against myself for being lazy.
Finally, those who follow classical lit will know of the "Landmark" series. These are big editions of the great Greek histories, with a wealth of maps and illustrations. They've done Herodotus, and Thucydides, and now they've done Xenophon's Hellenica. This is important because the only translation out there is the old Oxford version which sucks ass. This translation is not great but it's way better. And the maps, etc., are a huge help.