It works very effectively, scaring readers with his potential and allowing imaginations to run wild, as a book should do.
In the book, he is immediately scummier and more obviously scary than in the movie.
The movie Psycho is mostly faithful to the book, though a lot of the details of Norman Bates, the troubled killer in both, are changed.
In the novel, Bates is also a slovenly drunk who immediately makes readers wary of him, whereas in the movie, he is presented as somewhat clean cut and normal before being revealed as the killer.