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.
YMMV: Fahrenheit 451
Death of the Author: Later in life, Bradbury claimed that the book is really about how much television sucks. Shallow television programs, used to placate the masses in the absence of deeper reading material, is certainly an element of the story, but the more popular reading is to view it as one facet in a larger critique on censorship. At one college Bradbury visited, the students attending the reading outright told him his interpretation was wrong.
But then, it cuts both ways. "The man who does not read good books has no advantage over the man who cannot read them," as Mark Twain said it, which presumably includes the man who won't.
Ensemble Darkhorse: Clarisse enjoyed a similar fate to Sherlock Holmes', as her popularity among readers and their interest in her ambiguous fate in the novel prompted Bradbury to follow the film's example and reveal she's still alive at the end of the stage play.
Fan Dumb: Some people thought it was unfortunate that Bradbury gave his blessing to the book being released for electronic book readers such as the Kindle, missing that the point of the book is about the act of reading, not about the alleged value of bound volumes of paper and ink.
Montag coming home to find Mildred unconscious from a drug overdose (and the uncaring doctors coming in to pump her stomach).
Heck, the entire premise counts.
From the movie (during the scene of the old lady burning her own house so the firemen can't arrest her): "Nine elevenths are ninety-nine, nine twelfths are a hundred and eight, nine thirteens are a hundred and seventeen, nine fourteenths are a hundred and twenty-six..."
Special Effect Failure: The "jetpacks" in the film are very shoddy. Apparently they couldn't afford real helicopters.
Squick: Besides the Family-Unfriendly Death, there's also the scene in the novel in which Millie gets her stomach pumped after an apparent suicide attempt. This one is specifically called disgusting by the narrator.