Marneus Calgar is a 5 issues comic in which we get to know the origins of this Ultramarines chapter master. Meanwhile directing a battle against chaos forces, Marneus explains his youth and how he got chosen to became a Space Marine to an Adeptus Mechanicus ally, combining flashbacks with "present action".
The quality of the drawings is excellent, with no problems on depicting some gory scenes. As for the story, on one side the origins are quite interesting, I won't spoil the surprise but it is quite unexpected what we learn, specially for the Ultramarines chapter begin so based on laws, code and rules. On the other side, the situation becomes quite absurd, a too talkative chapter master telling a story to an adept which sometimes seems to be more interested in the actual war than Marneus itself. It feels almost absurd that he would go and tell a very profound secret to a random unknown ally, even more so during a battle, no matter how incredible he is calculating strategies to defeat the enemy.
I applaud the desire to create genuinely new content (even if coming from known characters), and a really grim and dark tone more akin to the Warhammer 40,000 setting, but the scenario and way to tell it feels too much forced. That said, it is interesting and seems that Games Workshop is really trying to push the lore component forward and make it way more complex than until now.