It's difficult to get into all the details without spoilers, but suffice it to say the Soviet Union does not appreciate the use of nuclear weapons against its ally China, so Stalin takes advantage of the situation to not only retaliate against America's allies but eventually launch a full scale invasion of Western Europe. Before the novel is even one hundred pages finished, the Soviets and Americans have nuked each other a dozen times over.
It's a Turtledove novel. If you're at all familiar with his work, this novel contains the usual stilted dialogue. Thankfully, Turtledove seems have given up writing sex scenes. Two things he does very well is portray the effects of atom bombs on cities and radiation sickness in civilians, and every day life in Stalinist Russia. He emphasizes how Soviet citizens teach themselves crimestop: they know what is true but they know better than to say so out loud. Here in the United States, speaking the truth can get you fired or socially ostracized. In Soviet Russia, it gets you sent to the gulag or killed. Two characters are listening to the radio after a major Western European city gets nuked. One of them says, "They make 300,000 deaths sound like such a big number. That's a slow day for Comrade Stalin." Turtledove is also great at communist propaganda-speak: "Forward, progressives of the world! Forward to victory against the reactionary imperialist dogs!"
The story is pretty depressing even by Turtledove standards. As per usual, there are dozens of viewpoint characters which makes it difficult to keep track of the entire cast. Stalin makes several appearances but we never get inside his mind. Truman is one of the viewpoint characters and you get to see how the use of several dozen atom bombs begins to weigh deeply on his conscience. I give it 4 out of 5 stars. Would nuke again.
Any blog entry about the Soviet Union makes Hell March mandatory: