I'm halfway into the two towers.

The movies are really quite similar. The only ways they are different are, in my opinion, better.

Aragorn being more "down-to-earth" and less focused on reclaiming the crown feels a bit odd, especially when the last movie is called "return of the king" but with the extended edition scenes of him and Boromir speaking about it does make it a bit better. Though, without the extended edition you feel as if he only became king because he wanted the ghosts on his side.

What I love the most is the additional involvement of Sauroman, it's great, in the book he's kind of a bore, a character the movies did a great deal to improve upon.