I'm not a fan of doing book to movie comparisons. I figure that film and literature are two different art forms, so I shouldn't compare their rendering of the story anymore than I would compare the same story as presented in a painting as opposed to a ballet. So I tried to take the film on its own merits (admittedly difficult to do, since I watched the movie on the same day I finished the book), but even at that, I think the movie falls short.
Clift plays George Eastman, poor nephew to a rich, socially elite family in a small New York state factory town. He's been invited by his uncle to come and work in the Eastman factory, giving him an entre into a world of luxury that has always been out of his grasp due to his family's humble position (they run a mission and preach on the streets). George strikes up a love affair with Alice Tripp (Shelley Winters), a girl who works with him in the factory, but his attentions for her quickly fade when he becomes interested in Angela Vickers, another member of the rich set, played by Liz Taylor. Complications ensue, and George finds himself and his situation spiralling drastically out of control, with an ending more tragic than he ever thought possible.
George Stevens directs the film with a sure hand, and there are some breathtaking displays of directorial skill. For example, one that stands out in my mind comes when the camera focuses on a radio reporting a possible murder, while the young, rich kids with whom George has struck up a friendship goof off in the water in the background. There are also some great uses of dissolve editing, though the technique is somewhat overused.
But there are many problems with the film, notably its pacing. Much time is spent on George's love triangle with Alice and Angela, while the script races through the trial and George's ultimate fate, as if the screenwriter realized he only had two hours to tell his story when he'd already wasted an hour and a half on front-end material. Rushing through the end blunts much of the story's original intent and power, as that is where the majority of moral questions arise.
Also, the character Shelley Winters plays is so drab and mousy, that one doesn't understand why George would entangle himself with her in the first place. But Clift does a great job with the lead role, delivering a performance of raw nerve.
It befuddles me somewhat as to why this movie is quite so acclaimed. I can only imagine that its reception has to do with cultural moods at the time it was released and that it just hasn't aged well. It came out in 1951, a big year for literary adaptations ("A Streetcar Named Desire" and "Death of a Salesman" were both given big-screen treatments that year), and you only need to compare "Sun" to "Streetcar" to see how short it falls at capturing the essence of a ture literary classic.