I've read the book, haven't seen the movie yet.
In defense of adapting from books to movies, things will inevitably have to change. It's just a question of what works for a particular medium. I remember as I read the book, I thought some aspects would be perfect for a movie; and others would be very difficult to make work. (Though it's been so long, I don't remember what those details were...)
By hoping that a book adaptation is going to be 2.5 hours, you're pretty much setting yourself up for significant disappointment. Studios want two hours or less - because once you go over, that cuts into the number of screenings you get in a day.
However, learning that they switched out a lot of the references in the book to resonate with younger audiences is disappointing. (Though, I suppose, understandable.) Don't tell me they took out Zork!?
I'll have to watch it and decide for myself, I guess. :)