I have read Blood and Iron, the newest addition to Turtledove's series, and it was very interesting. The book spans the years 1919 to 1927 in the aftermath of the Great War.
As those who read the series probably know, the US and Germany end up winning the Great War in 1917 in Turtledove's alternate history. The Confederacy surrenders as Yankee "barrells" (tanks) slam through the South, and Canada follows soon after. The French Mutinies are far more devastating in this world, with the French ending up surrendering soon after the Russian Revolution. England then ends up surrendering as the US navy finally closes the sea gate between Canada and Britain, and the High Seas FLeet is finally able to break out of the North Sea soon after the fall of France.
The US and Germany end up solving the "Irish question" for Britain. Britain is forced to give up all of Canada to the US, and Quebec and Ireland are freed as independent republics. A rebellion breaks out in Northern Ireland as the Protestant rebels refuse to unite with the rest of Ireland. Defeated Britain is forced to stand by while Irish troops quell the rebellion with support from the US and German navies.
Meanwhile, in the defeated and embittered Confederacy, Jake Featherson spreads his message of hate and revenge through the new fascist Freedom Party.
The victorious US meanwhile enjoys new hope and prosperity, but continued labor strife results in Socialist Upton Sinclair being elected President in 1920.
Also, the US and Confederacy both begin testing new battle tactics by supporting the various conflicts in Latin America, such as a civil war in Mexico, where Confederate supported government forces fight US - backed rebels.