My uncle has gone through some tough times lately and I'd like to give him something that will pleasantly surprise him. He's into WWI/WWII, general European (Henry VIII/Elizabethan times), almost anything war-related. Trying to keep it under ~$100 but if it's friggin amazing I'll stretch. Thanks!
Has he read Hiroo Onoda's No Surrender: My Thirty Year War? That book is incredible, very readable, and not as well known as it should be.
If he hasn't already read it, Guns of August might be my favorite book of all time, including fiction. I just bought one to add to a secret Santa gift myself.
Patrick Geary's "The Myth Of Nations" is an inexpensive add to any gift. It's a fun, quick read that neatly introduces the idea of just how much of what is popularly taken for granted as a national lineage or identity in major European cultures was deliberately manufactured in the eighteenth-nineteenth century, as a means of solidifying potentially illegitimate-seeming nation states. By the time you get to the major points of crisis in wars and the like, you can see the influence of those once-obscure or wholly invented ideas becoming part and parcel of the "nation's" sense of what was worth dying over.
That's my recommendation, off the top of my head, as I'm more inclined to go with something provocative and punchy for a gift.