These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
After the M.M.s haul Doremus off to Trianon, Emma seems more concerned about the mess they made than her husband's well-being. Is she a callous wife who is unmoved by her husband's incarceration? Or has she understandably stopped loving Doremus because he cheats on her with Lorinda and endangers their family with his activism?
Harsher in Hindsight: The book was written in the early days of the Nazi regime, and yet proves eerily prescient.
Iron Woobie: Doremus. He lives under a totalitarian state, sees friends and loved ones die, endures torture and incarceration in a concentration camp, and spends a lonely exile in Canada upon escaping said camp. At the end of the novel, he returns to America to teach members of the resistance, but is constantly on the run to avoid Corpos. Even in a best case scenario, it will be years before he can safely see his friends and loved ones again. And yet, he perseveres without self-pity.
Moment Of Awesome / Nightmare Fuel: When Shad is imprisoned in the Trianon camp, several of his former victims conspire to kill him. Through a ruse, they set Shad's room on fire. The screaming, terrified Shad burns to death, and his corpse was so badly burned as to be unrecognizable.
Once Acceptable Targets: Gay men. The novel depicts gays such as Lee Saranson and several unnamed M.M. men as depraved, promiscuous villains. In a more modern work, such depictions would be deemed homophobic.
Note that Ernst Rohm, one of Hitler's early supporters and a key figure in the Nazi Reich, was a pretty "out" homosexual, so Sinclair may have based Saranson on him.
Lee Saranson is basically an Expy of Rohm, who actually did have his own conflicts with Hitler. Part of the motivation behind the Night of the Long Knives, which took place not long before this book was published, was the perception that Rohm was wishing for more power. It's not helped by the fact that some of what fueled the paranoia was his own words—complaining about having used political means instead of violent revolution may have been merely rhetoric for public consumption, but still...
Paranoia Fuel: The novel resonates to this day because tyranny could happen here.
Squick: The torturers at the Trianon camp force-feed Doremus a large quantity of castor oil, which has a predictable (and gross) result. (The castor oil treatment was a favorite of Mussolini's Blackshirts.)
Values Dissonance: The novel's homophobia may seem jarring to modern readers who accept LGBTQ people. The only gays in the novel — Saranson and several unnamed M.M.s — are depicted as depraved villains. See Once Acceptable Targets above.
Values Resonance: The Windrip regime's racism toward blacks and Jews is depicted as bigoted, during an era when such bigotry was more commonplace in society.
Also, the novel depicts feminism favorably and has several strong, intelligent female characters. Lorinda, Sissy, and Mary are all brave, active, politically-conscious women. Lorinda in particular was a feminist activist in her younger days, and spends part of the novel secretly teaching a group of working-class women.
The novel takes misogyny and sexual violence against women seriously. When the Windrip regime robs women of jobs and rights, it is depicted as unjust. Similarly, M.M. acts of violence against women are rightfully depicted as atrocities.