I like the premise. Basically, Hogan gives us three possible timelines. In the original timeline, a utopian future develops in the 21st century--one that never knew the horrors of the second World War and the cold war slowly melted into a "third way." But EVIL oligarchs unhappy losing power in 2025 use a newly developed time travel device to try to swing things their way. They use the limit of their reach--a century in the past, and decide to use an obscure house painter to their ends--Adolf Hitler. This creates a new timeline, one where by 1975 America, along with Australia and New Zealand are the last free outposts in a Fascist world. Except an escaped scientist having let the Americans know how their future has been tampered with, they decide to go back into the year 1939 in a last ditch effort to save liberty and democracy--picking an obscure politician to change things around--Winston Churchill. The premise reminds me a bit of Harry Turtledove's The Guns of the South, where time-traveling White Supremest Afrikaners try to change the outcome of the American Civil War. Except Turtledove is known as the master of alternate history for a reason. While Hogan spends a lot of time on the physics, the emphasis in Turtledove is on the characters, and his Robert E. Lee is much more memorable--and important to the narrative--than Hogan's Churchill. I am impressed by the research Hogan had to have done into political and scientific history to weave two alternate histories, and it's entertaining enough to read once if you like reading alternate history, but in the end this isn't a memorable, strong enough work I consider it a keeper.