I'm also reading, What If?, a book about alternate-history, written by historians. Yeah, I can go to alternate-history forum, and read a lot of ideas, but I like reading alt-history from published authors, especially historians. My mind is very impressionable, and the first alternate-history I read was online about how if only The Germans went into Moscow, in '42 and that stuck with me to this day.
I also use Alt-history, when running historical-games, well, historical-based, like World of Darkness games, that, I base it on, that, while all the supernatural stuff is going on, something unexpected happens in that particular timeline.
I read a scenario in which the Spanish-Armada followed their original plan and the Dutch-Spanish forces were able to land in Kent, and advance, with little resistance (other than untrained militia) to London. The author, pulled up another work of alt-hist., in which Queen Elizabeth was assassinated just prior to the siege of London.
Edit: and the scenario if the Arminius' trap failed in Germany, AD 9 was rather bland. Most of the chapter was about the events leading up, and, in the end, Varius just didn't fall for his trap. Yeah.