There's a good reason that, when I'm interested in new authors, I go for the earlier stuff first. It makes sense, chronologically, and it's fun [for me:] to see how they've improved. After reading through a bunch of Westerfeld's newer works, I read this one and instantly knew it was one of the first. 
 It's a pretty cool concept. There's a 25th hour of every day in which time stops, and only certain people can experience it. And it goes through all the cool and terrifying things that happen during this time. I had a difficult time grasping onto the characters, though; I'm hoping they develop more in later books. I don't really know who the midnighters are, don't have a real feel for their personalities beyond who they are during the secret hour. 
 But it's a fun little read, and I need to own the rest of the series. Then I can properly judge.