I can sum up this book in one word, but I think that would be unfair to the author. With such a high rating and great reviews I high expectations for this book. Unfortunately I found myself reading a rehash of Romeo and Juliet.
The plot was mildly interesting, but the characters and the world building was not. I felt the author was trying way too hard to make Karou different from other girls, which subsequently backfired into making the character a rather dull one. I wouldn't call Akiva the man of my dreams either and found his character to be rather wooden.
So, overall: dull.