[1] Sandstorm (2004)

[1] Sandstorm (2004)
[2] Map of Bones: A Sigma Force Novel (2005)
[3] Black Order: A Sigma Force Novel (2006)
[4] The Judas Strain: A Sigma Force Novel (2007)
[5] The Last Oracle: A Sigma Force Novel (2008)
[6] The Doomsday Key: A Sigma Force Novel (2009)
[6.5] The Skeleton Key: A Short Story Exclusive (2011)
[7] The Devil Colony: A Sigma Force Novel (2011)
[7.5] Tracker: A Short Story Exclusive (2012)
[8] Bloodline: A Sigma Force Novel (2013)
[9] The Eye of God: A Sigma Force Novel (2013)
[10] The 6th Extinction: A Sigma Force Novel (2014)
[10.5] The Midnight Watch: A Sigma Force Short Story (2015)
[11] The Bone Labyrinth (2015)