Still, once (if) the book appears, it will enjoy an innate appeal thanks to the counterfactual nightmare of the Nazis actually succeeding in developing a nuclear weapon and utilizing it during World War II against Allied forces.
In real history, British-trained Norwegian forces sabotaged Norway's heavy water production facility at Vemork (which the Nazis had taken over after their conquest of the country in 1940 and reactivated in their effort to produce the plutonium necessary for a nuclear weapon). The sabotage action (known as Operation Gunnerside) took place in February 1943 when Norwegian forces, braving winter weather, succeeded in infiltrating the plant and blowing it up.
Whether or not the film can be a dramatic success partly depends on whether viewers care about knowing the ending in advance. Perhaps many will be unaware of the story ahead of time, but common sense should make it clear to even the most ignorant viewers that the Nazis fail.
Even so, the possibility that the Nazis could have succeeded may suffice to make the film a dramatic triumph. A historical counterfactual may not have to be spelled out in detail -- it may remain latent -- for it to be effective. It may merely need to hover in the background to serve as a foil that underscores the significance of real history.