I finished "The Manchurian Candidate" several weeks ago. It was not what I expected, although it was fun. With the benefit of hindsight, I'm not sure if it was meant to be an over-the-top treatment or not. It's sort of like the anti-Strangelove: The novel "Red Alert," upon which Kubrick's "Strangelove" was based, is a thriller, but its tongue is nowhere near its cheek. The story I've always heard is that Kubrick found that the story was, on its face, so horrific that satire was the only way he could devise to make it bearable. (It's a very strange experience to read "Red Alert" and discover several passages that appear nearly verbatim in the film. There are no characters in the novel named Buck Turgidson, Bat Guano, or Jack D. Ripper.)
"Manchurian" is just the opposite: As much as you might think that the Frankenheimer/Sinatra/Saint film is pretty "out there" -- it had the bad luck to come out right around the time of the Kennedy assassination (the first one, before we knew we'd have to start numbering them like World Wars and Chicago albums), and was almost never seen for about a generation afterward -- I'm here to assure you it's not as far out there as the novel.
I can probably do no better than to point you toward the Introduction added to the 2003 version which I read:
The true artifact of cold war culture is the novel by Richard Condon that the movie was based on. Condon's book came out in 1959 and was a bestseller. It was praised by The New York Times (A wild, vigorous, curiously readable mélange") and the New Yorker ("a wild and exhilarating satire"); Time named it one of the Ten Best Bad Books -- which, from a publisher's point of view, is far from the worst thing that might be said about a novel."
Condon was a cynic of the upbeat type, not unlike Tom Wolfe: his belief that everything is basically shit did not get in the way of his pleasure in making fun of it.
Some people like their bananas overripe to the point of blackness. The Manchurian Candidate is an overripe banana, and delectable to those who have the taste for it.
Louis Menand, "Introduction"
The Manchurian Candidate (2003 edition)