"The Empress of Mars" by Kage Baker
"The Swastika Bomb" by John Meaney
"Just Like the Ones We Used to Know" by Connie Willis
first-rate novellas, all three.

The rest of them are OK, but your taste may vary from mine. I've never read an alternate history before (The Swastika Bomb) and I was fascinated by the level of detail and intrigued by the premise. Well worth your time.