Sigma Force

The Doomsday Key / The Last Oracle (2013)
Sigma Force Novels 1 (2014)
1. Sandstorm (2004)
2. Map of Bones (2005)
2.5 Kowalski's in Love (2006)
3. Black Order (2006)
4. The Judas Strain (2007)
5. The Last Oracle (2008)
6. The Doomsday Key (2009)
6.5 The Skeleton Key (2011)
7. The Devil Colony (2011)
7.5 Tracker (2012)
8. Bloodline (2012)
9. The Eye of God (2013)
10. The Sixth Extinction (2014)
10.5 The Midnight Watch (2015)
11. The Bone Labyrinth (2015)
11.5 Crash and Burn (2016)
12. The Seventh Plague (2016)
12.5 Ghost Ship (2017)
13. The Demon Crown (2017)
14. Crucible (2019)
15. The Last Odyssey (2020)