I wouldn't go into the Night Circus expecting a lot of action or a well-explained magic system, it's a lot more vague than that. But I did enjoy the author's writing style and the mysterious/magical vibe I got from reading it.
It's interesting to see how divisive this book is, looking at the Goodreads reviews, so I guess you'll either like it or you won't.
I had a couple of nitpicks:Tsukiko felt too much like a stereotype of a Japanese person, doing a tea ceremony, etc. and it feels like the author chucked her in for the exotic-ness of it, or made her Japanese to make her seem more mysterious.
There was no depth to the love story either - there's not really any reason for Marco and Celia to fall in love, other than that both are strong magicians dueling against each other. You could also see it coming from a mile away, so I was confused that Marco initially got together with Isobel, and stayed together with her for a long time. The break up between them didn't end up being that big of a deal either so it felt a bit pointless.