Doubling Down is a notable step up from Door Number Three. That's not to say that D#3 isn't good because it is, but there's a healthy amount of world building in it. This time out, the action is as intense and unhinged as the gang that staff Athenaeum, Inc. But, be warned, along with the action there unexpected moments of dark humor and reality that gives this book a degree of authenticity that humanizes the characters. As a rule, I try to keep spoilers out of my reviews, but I will say this...the blurb on the back barely scratches the surface of this rocket ride!