How Few Remain: A Novel of the Second War Between the States by Harry Turtledove
Published in 1997, How Few Remain is an alternate-history novel in which one pivotal event changed the course of the Civil War and the history of the United States. Though How Few Remain is a standalone novel, Turtledove has written two trilogies (Great War and American Empire) and a tetralogy (Settling Accounts) that follow in the same alternate timeline (dubbed Timeline-191 by fans).
