First was a Tom Holt novel, called Meadowland, in which two Varangian Guards tell a story about the Viking's arrival and attempted colonization of what turned out to be North America. Of course, it really isn't about history, but about people, and how they can mess things up. Pretty good read.
Second was Osprey Fortress #44: American Coastal Defenses 1885 – 1950, a discussion of many fortifications built at important points along our coast since the Civil War. I've actually been to one of the sites discussed here, just north of the Golden Gate Bridge, and I found it a moment of wonder to gaze out to sea from the gun emplacement. Interesting read.