The book felt like a direct continuation of The Talon of Horus from Fabius' perspective. So I am having a strong vibe that its set in the same time period, which makes sense as its a trillogy and giving Fabius time to grow.
I wouldn't be so sure of that. The Shattering that occurs in Fabius Bile is set around M34, while his meeting with Abaddon occurred prior to the 1st Black Crusade which happened in 781.M31. I think this may be an example of Warp time-dilation, what feels like a short time to Fabius has in fact been three thousand years to the Imperium.
I too found Fabius to be a wonderfully dark read, very funny and entertaining, and carrying Reynolds' trademark epicness. Not every BL author can capture the madness and variety of Eyespace, the realms of Chaos and the vistas of horror and wonder within them, but Reynolds does it expertly. But the real achievement here was he made a character whose rooted in real-life figures like Josef Mengele and other such monsters into a likeable, understandable and even relatable three-dimensional character. I would never have thought that altruist or the phrase "one of humanity's most ardent defenders" could be used to describe Fabius "The Butcher of Terra" Bile, but wow. This book truly reshaped how I view Bile, he's so much more than the mad scientist of the Legions, oh so much.
Really i'm loving the recent trend in BL in writing the Chaos Space Marines as more than just greedy psychopaths. Ahriman, Abaddon and now Fabius all have their own series either completed or in progress and each one has been fleshed out and revealed as much more than the codex's paint them. Ahriman, a misunderstood scholar trying to fix his mistakes. Abaddon, a warrior and leader who envisions a new dawn for the Astartes. And Bile, a scientist who works to see that humanity survives the galactic conflagration that is Chaos. I'm eagerly awaiting the Lucius series that is upcoming, and really curious whether Ian St. Martin will find a way to make Lucius likeable, or just preserve him as that narcassistic jerk who killed Solomon Demeter.
My two favourite parts of Bile's debut novel were when Bile himself shot another EC in the crotch, and the Noise Marines having a rock concert complete with stage dancers prior to battle.