It’s the intro on pretty much every 40k book there is (Edit - not on A Thousand Sons, that has a different intro, so probably not Horus Heresy and the like, anything occurring in the 30k era).
I just checked my copy of the first Ciaphas Cain novel as well as Wreck and Ruin (Sister of battle novel) and it’s copied essentially word for word.
It’s the intro on pretty much every 40k book there is (Edit - not on A Thousand Sons, that has a different intro, so probably not Horus Heresy and the like, anything occurring in the 30k era).
I just checked my copy of the first Ciaphas Cain novel as well as Wreck and Ruin (Sister of battle novel) and it’s copied essentially word for word.