The two stars are solely for the tensely woven plot and the well-crafted action sequences. Sadly, for an ax-military who should know better, Chris Ryan commits some serious and basic factual errors, the most glaring of which is his main character Josh building "landmines" out of shotgun shells amazingly left behind in a sheriff's office in 1924, some 80 years earlier than the action of the novel and, even worse, making bombs strong enough to mangle steel and tear limbs off people out of -- wait for it-- glass bottles filled with 80-year-oldheating oil and nails! Clearly Ryan hasn't even the most basic knowledge of chemistry (and neither does his editor, nor it would seem does either of them have access to Google.
As regards the twists and turns of the plot, they are mostly good, but the denouement close to the end is amateurish and unconvincing.
No, this is by far not Ryan's best, and I actually feel cheated having spent three days reading it when I could have been spending time with a worthwhile book.