If you're not familiar with the film, GET FAMILIAR. It's Alfred Hitchcock, Laurence Oliver, Joan Fontaine, Dame Judith Anderson, Reginald Denny, George Sanders, Gladys Cooper, Nigel Bruce, Florence Bates... and it's amazing.
But in case you're not familiar right this moment, Rebecca is the story of the second Mrs. de Winter - a young thing of 21 who meets a brooding
The novel pretty much reinforced the way I feel about the film. For the most part, that's due to Hitchcock's mastery: his casting is perfect, his direction is perfect...there's little I can say about the film that would separate it from the book. It's also partly due to the fact that the novel is written in the first person, from Mrs. de Winter's point of view, and therefore is a lot of internalizing and psychological examination, which can be succinctly portrayed in a film.
There are however, some key differences that, while they don't deter, certainly make me see things differently. For one thing, for the most important thing, is Rebecca's death. I won't spoil it for you, but the film refuses to take one final step in her death that the book does not, and that step provides multiple levels of character that are therefore not present in the film.
The other difference is Mrs. Danvers' behavior. In the film, she's made more aloof, more creepy, and it deals with her in the end as you would deal with a living, breathing artifact of the evil Rebecca's presence. But in the book, she's more human... which is almost scarier.