Fortress #65: The Forts of Judaea 168 BC - AD 73: From the Maccabees to the Fall of Masada. I especially liked the artist's conception of what Masada looked like in its heyday. Having visited there, it meant a lot to me.
Campaign #212: The Six Day War 1967: Sinai. Again, it gave me more of the political background, teaching me details that I'd never known before about the war. Nice piece of work.
Campaign #222: Salamis 480 BC: The Naval Campaign that Saved Greece. You know, like Thermopylae didn't, really. They have photos of a real working trireme, to boot!
Fortress #50: The Forts of Celtic Britain. It gives a picture for the mind's eye for some of Bernard Cornwell's recent books, as they deal with these very sites.
Warrior #94: Polish Winged Hussars 1576 - 1775. I admit it, I read this one just because hussars are so damn ostentacious, and these Polish ones are no different from the general run of hussars. Outrageous uniforms.