tbh, I've noticed that with most books they turn into a film / TV show - the whole story gets changed slightly. But I think personally they have to bring more substance to the show than what is in the books - the books alone wouldn't make a show, there's not enough there IMO. The twilight books where the films have stuck quite close to the books I find a bit boring even though I loved reading the books - I guess there's not enough going on for a film. I'm not sure I'm putting across very clearly what I'm trying to say - but sticking true to a book is not always a recipe for success for a film / tv show, even though the book readers probably mostly love it..
I try and just enjoy the show and read the books afterwards, then I have nothing to compare it to. It would annoy me if I read the books first. I did that with Harry Potter, and then it irritated me so much when they didn't stick to the book.