The men and women of Ember return in an exciting book. Most exposition is removed thanks to everyone being introduced in the first book. The villain from "Tier One" also returns, and he is mad.
The story works as adventure, but doesn't make a case for the US Government pouring more funds into counter terrorism. Characters are given more to do, but little personal life reflects. Read for the adventure and hope in the next book that we get a little more personal with some of the characters.