I had real alternative scenarios in mind when I started the thread, but fantasy is okay, as long as it’s well done.
I didn’t particularly enjoy YOR&S, mostly because of the reincarnation aspect, but I did perservere because I felt part of the conceit (reincarnation) tied into the concept of an alternate world-view.
My understanding being that if Europe had succumbed to the Black Plague, would history itself be recorded the same way, or would we view history from a different perspective? so while we would perceive the reincarnation aspect of the story today as so many spacebats, would we feel that way if the world had developed in an alternate fashion.
(again - I didn’t like the book, and found the reincarnation aspect to be tedious and, at times, ham-fisted, BYMMV).
I just finished Michael Chabon’s The Yiddish Policeman’s Union. It’s an alternate history where a Jewish settlement it created in Sitka Alaska in 1940 and Israel is created and quickly destroyed in 1948. It’s framed as a murder/mystery. I really enjoyed it.
Another vote for Harris’s Fatherland. President Joseph Kennedy plans a summit meeting with the Fuhrer in 1964 Berlin, and an SS detective investigates a series of murders of old Nazis. Very, very good stuff.
Another vote for the Tsouras books, although they’re pretty dry, reading more as straight history than as novels. His alternate-Gettysburg book is quite good.
Another vote for Dick’s The Man in the High Castle, although I thought it was particularly implausible that the Japanese and the Germans carve up and actually occupy the entire U.S., which IMHO was well beyond their resources.
I’d also recommend Len Deighton’s SS-GB, about Britain under Nazi occupation and the German A-bomb project and a plot to bust King George VI out of prison.
Jerry Yulsman’s Elleander Morning is a fascinating, wry novel about Hitler’s murder while he’s a starving young artist in Vienna, and the very different but still recognizable world that unfolds without WW2.
The best American Civil War alternative history I’ve ever read was by MacKinlay Kantor, a Pulitzer winner for Andersonville. He wrote “If the South Had Won the Civil War” for Look magazine in 1960; it was later released as book. Here’s what happens: Grant is killed in a horseback accident during the Vicksburg campaign, and the Union makes key errors at Gettysburg. The Confederacy captures Washington and wins its independence. The U.S. has to move its capital (to Columbus, Ohio, which becomes New Columbia) and has no money left over to pay for the purchase of Alaska, which remains in Russian and, later, Soviet hands. Lee, Longstreet and in time Woodrow Wilson all serve as Confederate president. The U.S. and C.S. make common cause in WWI and WWII, and at the time of the centennial of Southern independence are once more discussing reunion. Kantor tells it better than I can.
Meh. It’s overrated in every universe, IMHO. 
Second vote for this. IIRC,
Texas declares its independence from the CSA, and the reunion talks with which it closes are between USA, CSA, and RoT.
Wow, that’s quite a long list of books and websites to work though. Thanks.
A personal favorite if you can find a copy is The Divide by William Overgard. Germany and Japan won WWII and occupied and divided the United States. The novel is set thirty years later when Germany and Japan arrange a summit meeting along the border and the American resistance plans an uprising.
Another underrated AH is Resurrection Day by Brendan DuBois. It’s set in the United States a decade after the Cuban Missile Crisis resulted in a limited nuclear war and ten years of martial law. It reminded me a lot of Fatherland for those who liked that book.
I’ve read both, and Fatherland is a far, far better book, IMHO. More internally consistent and much better written.
Polycarp, I believe you’re right about that particular detail of If the South Had Won the Civil War.
Obviously it’s a matter of personal opinion. But I’m surprised that you found one book “far, far better” than the other when I found the two to be so similar.