The characters aren't particularly complex or fleshed out, and because of the time dilation associated with the circus there's no urgency. But the sensory imagery is incredibly rich, and in that regard the impoverished characterization and lack of urgency contribute to The Night Circus's "photo album" quality -- readers get to wander through a particularly gorgeous photo album, but it belongs to a stranger so there's only a loose sense of how the photos fit together. (Thus the frequent comparison to Steven Millhauser?)