Whimsical. Fantastic. Amazing. A fairy tale of broad depth and scope, bottling the wonder of the old world turning into the new at the turn of the 20th century. It represents a conflict between big ideas and the small players that are affected by them; a true nature vs nurture concept while at the same time showing good vs evil.
Two magicians get two pawns as apprentices that they set against each other. This is an old contest between them, but this venue is new, and the most public it has ever been. The fly in the ointment, however, comes when the two fall in love with each other. This is very well handled by Morgenstern who charts the course of their romance in a way that takes place over years rather than days or months as someone involved with a romantic work such as this might be tempted to do.
She also works the perfect line of giving rules and guidelines for her magic while at the same time keeping the magic actually magical. There is no 'tapping an alternate plane of existence for energy' or any of that kind of postmodernism...its just MAGIC and it just is. Sure it is described as 'a different way of doing things' but that still might as well be MAGIC. And, so the legend goes, the more people who know it, the less powerful it is.
In a book such as this, the delightful thing is that you don't know if it will end well for our heroes, or badly. It is a fairy tale but more of the Terry Gilliam or Charles De Lint variety; old school. The characters are all very well rounded, and eventually become more and more aware that they are pawns to pawns in a game over which they have very little control.
Her greatest achievement for the book, however, is that it makes even the most well traveled or cynical of us want to visit the Night Circus. It is the kind of book that screams for a movie so that we can see with our actual eyes what our mind's eye has painted for us, and it will never quite live up to the expectations. The prose is magnificent, as is the pacing and the plot.
I highly recommend reading it.