The biggest difference for me was the sidekick that went with him to Dallas. Jake had to do everything in the book which I really liked. And the addition of this character in the show really ruined it for me. I've already ranted enough about him so you can read my previous posts if you like. I just didn't like that a lot of main points hinged on the ineptitude of that stupid kid.

Now you should go read the book. It really is phenomenal and extremely well written. I'd highly recommend it.