Thanks for all the suggestions!
I never knew something like this area of fic existed until recently. It sounds like a wonderful and intelligent diversion.
I think I will start with the 1632 that came so highly recommended and take it from there.
Thanks!
Roma Eterna by Robert Silverburg is a collection of stories about a world in which Rome did not fall.
British actor Stephen Fry wrote Making History–what if Hitler’s birth was prevented? With some twists…
Previously mentioned & highly recommended: Eric Flint’s series starting with 1812: The Rivers of War is a treat for Sam Houston fans. (I’m one.) Warning: the series is not finished!
The Peshawar Lancers by S M Stirling is a truly ripping yarn. Especially for Kipling fans.
And Dick’s The Man in the High Castle is one of his best books & a classic.
A lot of good suggestions here.
FWIW, both Eric Flint’s 1632, and his 1814: The Rivers of War are available as free e-books here.
A couple other books/series I’d suggest:
It’s hard to avoid mentioning Harry Turtledove for this sort of thread, because he’s written so much alt-his. Some of it better than others.
I’d give his WorldWar series, an Alt-his that begins with an alien invasion beginning in 1942 high marks. The first four books are the most ambitious, with characters all around the world to give a view of the whole conflict. The first book is In the Balance.