Does it seem like MOST of this book is

merely world-building? It kind of bums me out, particularly because we don't really get another chance to see the world for what it is until the comics finally had come out.

Am I off here?

I think you are. You find out a good deal about Roland's world in later books. If that's what you meant by 'world building'. If you mean, is it just introductory, then, again, not really.

Spoiler:

There are things in this book that have ramifications later in the series.

Well I started out by reading the second book, then the third then went back to the first... But it's definitely worth the read... It adds to the mystery of the charcter.