Other than Norman being a Tubby Trooper in the book instead of the Starved Stanchion he is in the movie and television series, I found no glaring differences between the Hitchcock film and the book. I can't even say that the book is better than the movie. They are completely equal in my eyes. Now the sequels? I haven't a clue. I have not seen the later movies, nor have I read the follow-up novels Bloch published (Psycho 2 and Psycho House). Now that I've tackled the first book, I feel comfortable moving on. Just wanted to make sure there weren't any differences.
Paul Michael Garcia does a terrific job with the Blackstone Audiobook. I don't know if there are other versions out there, but I enjoyed PMG's performance. This one comes in at 5:22 hours, so it's a little less than 3 hours if you bump up the speed. Worth a try.
In summation: A classic. The big reveal gave me chills even though I knew it was coming. Recommended whether you've seen the movie or not.
Final Judgment: A perfect argument for poor hygiene.