Well, 'The Dark Angels Omnibus' is a great pick. It contains multiple stories that give a comprehensive view of the Dark Angels. You get to see their battles, their internal politics, and their search for redemption. 'Angels of Darkness' is also a notable novel. It really explores the darker side of the Dark Angels, their hidden agendas and how they deal with threats both external and internal. 'The Lion' is a good one too as it goes back to the origins of the Dark Angels and their primarch.
Definitely 'The Unforgiven'. It's a classic for Dark Angels fans. It reveals a lot about their history and their quest for atonement. Another is 'Ravenwing'. If you're interested in their mobile strike forces, this is a great read. Then there's 'Azrael' which gives you an in - depth look at the chapter master's character.
It's about the Dark Angels, a First Founding Space Marine Legion, and their Primaris Marines. It likely delves into their history, battles, and the secrets they hold. Maybe it shows their struggle against the enemies of the Imperium and how the Primaris Marines are integrated into their ranks.
The lore. They are filled with rich lore about the Dark Angels. Their history, their traditions, their secrets. All these elements make the novels special.
The main characters are likely to be the Dark Angels themselves. They are the focus of these short stories, so we can expect to see Space Marines from this chapter as the central figures.