I like Kim Stanley Robinson’s The Years of Rice and Salt. I really wouldn’t go as far as calling it a good book exactly (the writing and the characters are kinda clunky in places, which is a bit of a thing with Robinson’s books in general), but I absolutely love the world-building

Roma Eterna by Robert Silverberg. The Roman Empire never ended, and it’s a collection of stories at various points of history.

It didn’t exactly start out as alternate history per se, but I liked Charles Stross’ Merchant princes series. He also recently added three new books to it and sorry of concluded it.