The author has two length action series going at the same time. with his Monster Squad [the Hard Case series] and and his Unholy Trio [the Cold Blooded series]. Both series had been going for at least a half dozen novels before he began to join them together in crossover events. This does not mean the two teams become one. Instead, both teams operater on their own as before but sometimes work together on an ad-hoc basis.
According to the author, the sequence of crossover events are:
Hard Case and Cold Blooded Crossover Sequence
1. Hard Case Book 7: Red Waves
2. Cold Blooded Book 6: Red Horizon
3. Hard Case Book 8: Kingdom of Hell
4. Cold Blooded Book 7: Hell on Earth
5. Hard Case 9: Isle of Darkness
6. Cold Blooded 8: Rule of Nightmare
7. Hard Case 10: No Mercy
8. Cold Blooded 9: Bloody Justice
9. Hard Case 11: Killing Field
10. Cold Blooded 10: Hell's Half Acre
11. Hard Case 12: Climate of Chaos
12. Cold Blooded 11: Blood and Honor
13. Hard Case 13: Raging Fury
14. Cold Blooded 12: Paint It Black
15. Hard Case 14: Cold Harbor
16. Cold Blooded 13: Cold As Ice
17. Hard Case 15: Hard Choices
18. Cold Blooded 14: Bloody Hell
19. Hard Case 16: Live By The Feud
20. Cold Blooded 15: Political Genocide
21. Hard Case 17: Homefront Nightmare