Excellent category! I'm surprised no one mentioned it before. (Well, maybe they did and I didn't see it.) Granted, much of the alternate history I've read has been by authors that write predominately science fiction, so that might've been why.
It's off-topic for the week, but I'll toss it out there anyway: If you like role-playing games (and this one might be a good read, even if you don't), Steve Jackson Games is releasing a book called "Alternate Worlds", which is a setting for its new gaming system. It includes information and history about numerous other worlds (presented as if it were fact, not in a narrative with a plot). The folks who had sneak peeks loved it (I wasn't one of them), but these people were gamers, for what it's worth.
TS
Sorry, I don't have the Ping list on me, so I'm linking it here. I'll ping everyone to the other thread later.
TS