I tried to read the book before watching the movies but god, just bummed me out too much. That being said, I'm reinvigorated to try again now I've seen part 2. I might actually prefer it that way since, as you say, you can just see it all coming, might even ruin the movie experience a bit.

As far as I've heard, it's a very faithful re-enactment, on par with the LOTR movie adaptations. (fun fact: Tolkien hated Dune)