Eye of Terra: The Horus Heresy, Book 35 (Unabridged‪)‬

The galaxy burns at Horus' command, and a billion more lives are lost with each passing moment - though it was not always so. Once, the title of Warmaster stood for honour, loyalty and a fierce pride in the strength of the Space Marine Legions. But perhaps by following the myriad lines of destiny and defiance that were already woven around the primarchs and their sons, we may yet come to understand the bitterness that can eat away at even the most steadfast of souls....

Full list of authors includes Nick Kyme, Chris Wraight, Rob Sanders, Andy Smillie and Matthew Farrer.