Nathan Hunt Matt's description is pretty apt. It gets faster as you get more information and can understand what's going on more. At the end, there's all sorts of things going on and it's pretty epic. I mean that in more of the older sense, too. You need to pay attention in the beginning and the whole way through, though, or you will be confused.
Matt I would describe it as the "reading fantasy" equivalent of playing a video game on Expert Mode. Its very dense and doesn't give you much background in terms of how the world and the magic works. So, even though there's a lot of action, it's still kind of slow-going just because you're trying to figure out what the heck is going on.