The Last Oracle: A Sigma Force Novel (Sigma Force Series Book 5)
Black Order: A Sigma Force Novel (Sigma Force Series Book 3)
The Doomsday Key: A Sigma Force Novel (Sigma Force Series Book 6)
Map of Bones: A Sigma Force Novel (Sigma Force Series Book 2)
The Devil Colony: A Sigma Force Novel (Sigma Force Series Book 7)
Bloodline: A Sigma Force Novel (Sigma Force Series Book 8)
The Eye of God: A Sigma Force Novel (Sigma Force Series Book 9)
Sandstorm (Sigma Force Novels Book 1)
The 6th Extinction: A Sigma Force Novel (Sigma Force Series Book 10)
The Last Oracle and The Doomsday Key: A Sigma Force Bundle