Which is maybe not your cup of tea, Steve, because it's a revisionist history novel.

Lion's Blood (2002) is an alternate history novel by Steven Barnes.

The following alternate history novels are set in fictional universes prior to the present day.

A series of alternate history novels by Taylor Anderson.

The Divide is a 1980 alternate history novel by William Overgard.

Robert Conroy is an author of alternate history novels.

Stonewall Jackson has appeared in a number of alternative history novels.

Other alternate history novels based on the survival of the Roman Empire to the present day:

Follett has written many detective books and history novels.

Many of his future history novels have medical or scientific underpinnings, reflecting his medical training and science background.