Angels of Caliban

With the Dark Angels spread across a hundred systems, primarch Lion El'Jonson stands as Lord Protector of Ultramar though his true motives are known to few indeed, and old rivalries on the home world threaten to tear the Legion in half. But when word comes of the Night Lords' attack on Sotha, the Lion's brutal actions bring Imperium Secundus once again to the brink of civil war. Not even the most fearsome warriors of the Dreadwing, nor any arcane secret of the Order, can guarantee victory if he sets himself against his loyal brothers.

Read it because
There was no way Imperium Secundus was going to last (or we'd know about it in the 41st millennium, wouldn't we?) and this is the beginning of the end...

The eBook edition includes integrated illustrations of characters and events from the story, and an afterword that places the story in context within the series.