Way back in 2002, I picked up a 40K novel called Soul Drinker, by Ben Counter. I was amazed at how great the book was and couldn't wait for the more tales of this space marine chapter. Two years later the follow up Bleeding Chalice was released and continued the intriguing tales of this Chapter that turns from the Imperium of Man. The series continued over the next few years with the sixth and supposedly final book being released this year.
Over the course of the books the trials and tribulations of this chapter (that strays from the light only to seek redemption after realizing the trickery that led them down the wrong path) are detailed in action packed stories that leave you wanting more.
I'm not going to do a full recap of the books but in summary, Sarpedon, leds his chapter in conflict against the Adeptus Mechanicus, which leads to a chapter war. Becoming renegades they continue to fight with their own agenda eventually being tracked down and captured.
The sixth book, Phalanx picks up after that capture and attempts to tie up all the loose ends of the book. While I enjoyed the book, it really felt like the author was rushing through to tie up all the plot hooks he planted in the other novels. For people who don't like loose ends you'll be satisfied.
Some of the resolutions seemd to be a case of, "these are my characters, I'm ending this so there's no way anyone else can pick up the torch." Which is understandable, when the Gotrek and Feliz books continued under a different author, they didn't quite have the same magic as the older stories.