The Black Library discussion

Along similar lines, if anyone could suggest a sensible reading order for this new 40k lore-arc, that would be greatly appreciated. I've also been a bit out of the loop lately.

Mark wrote: "Along similar lines, if anyone could suggest a sensible reading order for this new 40k lore-arc, that would be greatly appreciated. I've also been a bit out of the loop lately."

Not really definitive as there is no "arc" in the novels and I myself and am still catching up, but....
The Emperor's Legion: takes place during and shortly after Gulliman's awakening.
Cadia Stands: takes place during the battle of Cadia just before Gulliman's return, but dosnt really delve into the bigger implications.
Dark Imperium: takes place after Gulliman's awakening and follows the Imperium during the years that follow with the introduction of the new Marines.

Shroud of Night, The Last Hunt & The Devastation of Baal, all take place post Gulliman's return, but I am yet to read those two so I cant give you a definitive time

Thats not everything but hopefully it'll give you a start to begin your reading search.

There is no 41k yet correct? That was an Imperial type-o right?

41k refers to The Beast Arises series that begins with I Am Slaughter. No typo. If you want to see how that begins when Roboute Guilliman is awakened you start with the Plague War series. First book being Dark Imperium. I have the audiobook and it was a great listen.