Nate Crowley
He is not Steve Parker.
Nate Crowley is one of the most recent authors for Black Library and has so far written three short stories for the 40K setting, all three of which have been rather nice reads.
The first was 'The Enemy of my Enemy' a story about Orks and Imperial Guard temporarily setting aside their differences to fight Tyranids invading a mining world they had been battling on. It also features a suprisingly realistic depiction of an Imperial Guard general so dedicated to fulfilling a legacy for himself and so delusional that he compares himself to Rogal Dorn at one point. He gets obviously betrayed at the end.
His second story is about an uneducated factory worker meeting a Space Marine and understandably having her whole world rocked.
The third and longest story he has written so far, entitled 'Severed' is a story about Vargard Obyron and his boss Nemesor Zandrekh on a tomb world where all Necrons within have had their minds erased and their bodies taken over by a massive supercomputer. It contains a scarily realistic depiction of Alzheimer's, a deepened look into the mental state of Necrons and how they feel about being reduced to unfeeling shells, and finally a large amount of gay undertones with Obyron claiming he loves his Nemesor several times. (The reader gets to decide if the love is of the Platonic variety or not.)