I will never forget that movie. I was a kid in the 70's. We were on vacation in Florida. Our parents left us in the room with that movie on while they went out. I was petrified. I am still scared from it! I can't read the book.
There've been about 5 Stepford movies, some are remakes and some are sequels. The very original is pretty close to the book. Each new remake gets further away. The book gives you more emotional info - the stuff they can't really include in a movie.