[darkreever]

I'm gonna go against the grain and say Hammer and Anvil, but only if you've already read Faith and Fire. Otherwise go for Angels of Darkness.

 

[darkreever]

Age Of Darkness is OK, I think that or Damnation of Pythos- maybe my love of HH is making that bias though...

He listed Angels of Darkness, not Age of Darkness. The first is a fairly old novel about a Dark Angel chaplain and the fallen, the second is about the opening stages to the Age of Darkness during the Heresy.