Gruber has yet to disappoint me. What I think I love most about his books is how he manages to immerse the reader in an unfamiliar culture and make it immediately accessible. I think I learned more about Central Asian/Islamic (specifically Pashtun) culture and politics from this book than from all of the news and political TV programming I've seen in the past 10 years. He also consistently tackles themes of identity, family dynamics, etc. - where (and who) we come from informs who we are, no matter how much we might prefer otherwise.
On introduction, you assume that Theo is "just" an American soldier assigned to an elite, special-forces-type unit, currently recovering from an injury received in the line of duty. Rather quickly, though, you discover that his background and family is an unusual one - his mother Sonia an author, peace activist, and Jungian psychotherapist; his Pakistani father Farid, son of a wealthy magistrate and power broker, now a university lecturer on international law. When Sonia disappears on her way to a peace conference in Pakistan, Theo is forced to reconnect with his history in that region, revealing hidden layers of his own identity in the process of rescuing his mother from a group of jihadists.