Harry Turtledove writes many different types of alternate history, some mixed with science fiction (Worldwar series, The Guns of the South), some with a fantasy element (Darkness series, Detina series). How Few Remain is straight alternative history; Turtledove changed one event, and then from this "branching point" a different world emerges. In this book, the Confederate States of America defeated the USA because a courier did not drop secret battle plans (as happened in our timeline). The CSA is a nation in its own right. 20 years later, the USA still seethes from their crushing defeat and economic downturn, and attempts to remake the Union again.
Using multiple viewpoints in short vignettes, similar to John Brunner's novels or John de los Passos' USA, Turtledove evokes the moods of different groups and geographies. And as in Worldwar, Turtledove introduces famous people whose lives have changed because their history diverged. Thus Abraham Lincoln lives past 1865 (our 4-year Civil war ended sooner in this timeline, with a different victor), but is disgraced for losing the war, and finds himself extolling the virtues of socialism. Teddy Roosevelt finds an opportunity to drum up a volunteer army at age 21, fighting the Brits in Western Canada.
Political intrigue and diplomatic tangles abound. The CSA aligns with England and France, while the USA forms a partnership with Germany. But the US is surrounded by enemies, with British Canada to the North, and the CSA with its new Pacific ports (having purchased two provinces from the Empire of Mexico). The USA is spoiling for a rematch, and President James G. Blaine, the first Republican elected since Lincoln, intends to avenge the loss of the Southern States.
How Few Remain is the springboard for Turtledove's Great War series, with a USA/CSA version of World War I thirty years later. These are followed by the American Empire series of the 1920s and 1930s, with the CSA playing the role of Germany in our timeline. While these books are enjoyable, none of them compares with the freshness and the fullness of HFR.
Several critics of Turtledove's novels, such as the six books in the two series mentioned above, note they are painted with too broad a brush, and painted by the numbers. This novel transcends the others' failings, though, by evoking a haunting sense of defeat and despair in his descriptions of the defeated North.