Science fiction writer Allen Steele submitted the story that would become 2014's V-S Day to a science-fiction magazine in the late 1980s and later expanded it from a proposed movie treatment into the current novel. He supposes that Nazi Germany researched and built a suborbital rocket bomber called Silbervogel and that the United States recruited Robert Goddard to lead a team that developed a counter-attack.V-S Day (the title refers to a "Victory-Space" day like the Victory-Europe [V-E] or Victory-Japan [V-J] days) describes the parallel research programs, largely through the eyes of Werner Von Braun and Goddard. Neither man wanted space as a theater of war, but Nazi battle plans made it one and they each find themselves sacrificing parts of their dreams on the altar of necessity.
Day is mostly a kind of techno-thriller race against the clock sort of story. Von Braun must convince the Nazi leaders that a rocket ship is a practical program and survive Allied attempts to destroy it. Goddard and his team must battle government myopia and the untested nature of their research to complete their own ship. There's some characterization, but not much, given the rather large cast. Given Steele's pretty thorough research, the novel doesn't feel all that "alternative" historically. After all, Chuck Yeager broke the sound barrier in a rocket-powered aircraft barely four years after Steele sets his flights, so what he describes is not particularly outlandish.
That said, V-S Day is still a good-quality yarn that doesn't waste your time and gives some neat insight into how researchers went about developing real rocket-planes a few years later.
In 1952, civil service functionary David Fitzgerald is a secret member of the Resistance, a group of English citizens and others trying to counter both their own growingly authoritarian government and its Nazi puppet-masters. When the movement learns that the brother of a scientist working on secret research in America is in an asylum, sought for questioning by government agents and the SS, it enlists David to see what can be learned about what the man knows. But the secrecy that his espionage has required has already driven David apart from his wife Sarah, and what's being asked of him now might be a final wedge.
Sansom focuses on how the slowly-growing power of the state has been sapping the life from the people of London, and how different agencies have been taking advantage of their expanded power to seize more as well as to hide their work from an increasingly frightened and cowed populace. Much of his novel seems have an instructive purpose: "To those who think, 'That couldn't happen here' about abrogation of civil rights and support for fascist and even Nazi ideals, here's how it might have happened here." He's also concerned with what he sees as the corrosive effects of extreme nationalism, figuring that Nazi Germany's success might spawn similar movements in other countries. In case you don't get that from the several speeches different characters give, Sansom spells it out more clearly in a concluding essay.
Dominion is a long novel and often seems longer. It begins with some seriously leisurely character introductions that slow themselves down even more by flashing back, and then when it begins its action portion it's an extended series of cliffhangers in a long chase scene. Think what an old Republic serial might be like if each 12-15 minute episode was stretched out to the running time of the full story. It won the World Science Fiction Convention's 2013 "Sidewise Award" for best long-form alternative history work printed in 2012, but considering that one of the other finalists was a silly story of "Christian theocrats" piloting airliners into the "Tigris and Euphrates World Trade Towers" in Baghdad and the resulting war and events, it could hardly do otherwise.
Douglas Archer is one of the Yard's keenest minds, but even he is unsure about a man murdered in a London flat which is obviously not his own. There is no identification on the man and there are no clues about his death, but even so the new German masters of the Yard seem very interested in the case. That could make Archer's work easier, or more difficult, depending on what he finds. And depending on whether other interested parties let him live long enough to find anything at all.
SS-GB is as much a mystery thriller as anything else. Different details about how Archer has to go about his business in a bombed and occupied London, and about what underground resistance fighters are trying to do give the book its other-history character, but the core is how Archer finds himself manipulated by people playing a much larger game than he realizes. This is often a theme for Deighton, who sees espionage as a matter in which those in the front are often working for people they don't know who have agendas they would never dream of. They will be the ones who risk everything, even though the cause for which they do so might turn out to be less of a truth than they realize.
Some of SS-GB runs improbably quickly, such as Archer's love interest and his own connection to the underground resistance, and some of the rest is sketched out less thoroughly than is best for the story. Deighton's never been one for bloat, but SS-GB could have used a sandwich or two to help its appearance. It's still a great read and a testament to Deighton's grasp of the ins and outs of espionage and the bureaucratic mess that often lies behind the cloak and dagger in the field.