I was very impressed by how the book chapters alternated between regular prose, and excerpts from newswire stories, inquests, other books, etc.
I don't know if anyone had used that trick before, but it got used since.
The original music, by Pino Donaggio, is what saved the movie (for me). I couldn't imagine the film without it.
It has been reissued on CD a few times, with some short dialogue clips, but the 1976 LP had only the music.
https://archive.org/details/carrie-1976Soundtrack-Vinyl24-bit