In fact, of the more than two dozen novels Kurland has written, only The Unicorn Girl, The Whenabouts of Burr, and his two sequels to Garrett’s Lord Darcy books are alternate history.

I may be misremembering, but isn't Perchance also an alternate-history story, or one that has alternate-history as an important plot point?

ETA: (Or maybe rather, parallel universes with alternate histories, which applies to The Unicorn Girl as well, IIRC)