How Few Remain is an Alternative History novel, about what would have happened if the South had won the Civil War. The American Civil War is the second most popular alternative History SF setting (the first is WWII) and a particular interest of Harry Turtledove cf the Guns of the South. This one has a far more credible reason for the South winning, the failure of McLellan to intercept Lee's battle plans during the Antietam campaign and Lee's victory there followed by foriegn recognition of the CSA. All of this is dealt with in the first few pages and is credible enough. But it's 1881, 20 years later, that is the focus of the book. At this point the CSA looks likely to acquire two Mexican provinces and thus gain a Pacific coastline. In order to stop this the USA goes to war.
Like most of Turtledove's books, the story unfolds from the viewpoint of a number of characters, in this case they're all historical characters. What's more we have George Armstrong Custer, JEB Stuart, Thomas "Stonewall" Jackson and Abraham Lincoln as viewpoint characters, all of whom died during the war or, in Custer and Lincoln's case, as a result of it. It's sort of fun to see them in 1881 meeting such people as Theodore Roosevelt and Albert Schlieffen (two more of the viewpoint characters.) It's also fun to see how Turtledove deals with how they would have coped in the world of 1881.
This is the major difference between this book and other alternative Southern Victory books. 1881 is the cusp of the modern world, a world with weapons of mass slaughter, industrial unrest, etc. The war the CSA fights in 1881 is very different to the war of 1861, which was bloody enough, because now every soldier on both sides has a repeating rifle. As such it resembles WWI more than the ACW. This is a foretelling of what is to come and indeed Harry Turtledove has written a series of sequels covering WWI wherein both the CSA and USA get involved.
This is more than just a prequel to the Great War series though. The book is well written, grabs your attention from the beginning and unfolds a story that is all too credible. This book is worth reading on its own merits and I reccomend it to anyone interested in the ACW, WWI, Turtledove's writing or just a really good story.