I got an e-mail earlier this week asking for what comics I'd recommend for anyone reading Vengeance and wanting to know the background on various characters and concepts Joe Casey is using in that series. I shared my 'essential' list with said e-mailer and he wanted more, so here's the essential stuff plus a few more suggestions if you're willing to do the extra work and maybe spend the extra cash...
The Essentials
* Cable #59-62 (introduction of Jack Truman)
* Deathlok #1-11 (more on Jack Truman and Larry Young)
* Uncanny X-Men #408-409 and annual 2001 (Stacy X first appeared in Casey's Uncanny X-Men run and these issues are the best and showcase her well)
* The Last Defenders #1-6 (how the Defenders you see in Vengeance came to be)
* Dark Reign: Zodiac #1-3 (the big Z himself)
Further Reading
* Uncanny X-Men #394-407 (the rest of Casey's run on the title, so more on Stacy X and the first issue has a young mutant that easily could have been the 'next generation Magneto' stand-in for Vengeance instead of the man himself)
* X-Men: Children of the Atom #1-6 (Casey writing teens and Magneto)
* Incredible Hulk #468-474 (Devlin Deangelo appears here)
* Heroes Reborn: Masters of Evil #1 (Casey writing villains being villains)
* Avengers: Earth's Mightiest Heroes #1-8 and Avengers: Earth's Mightiest Heroes II #1-8 (Casey writing the Avengers in a similar way to the Teen Brigade and using some of the villains that play a role in Vengeance... er, sort of)
* Avengers: The Origin #1-5 (the Rick Jones-era Teen Brigade in action)
* Iron Man: The Inevitable #1-6 (Casey writing about the balance between good/evil, order/chaos)
* Age of Heroes #4 (short, SHORT story by Casey and Nathan Fox featuring Zodiac)
* The Intimates #1-12 (from DC/Wildstorm and it's Casey writing about teens, more for the folks who love his take on the young folks in Vengeance)
Someone suggested proper annotations, but that's not my style.