Eventually, we’ll know how it all turned out. But even then we might still be — we might already be — haunted by the sense that things could have gone differently, for good or ill. The real question Roth was asking in “The Plot Against America” is “What if?” At a time of great uncertainty, that can be an oddly reassuring question as well as a scary one, if only because it can help to be reminded that uncertainty is nothing new.

Philip Levin’s early-1940s world, to those of us peering into it from our early-2020s vantage, looks both familiar and outlandish. The clothes and the cars, the cigarettes and the household arrangements evoke a period encrusted with mostly benign nostalgia, a hinge moment between one era and another, when Americans listened to Franklin D. Roosevelt on the radio and Pearl Harbor was just around the corner.

The ingenuity of Roth’s novel and the mostly faithful television adaptation created by David Simon and Ed Burns lies in the way this easy familiarity is twisted into terror. The series is at times almost unbearably suspenseful because most stories set in the years just before World War II are the opposite. History is by definition spoiler-free. (Unlike this article, which will divulge information about “The Plot Against America” and several other movies and television series.) We never stop arguing about what it means, but we pretty much agree on what happened next.