Chris Wraight
Leman Russ: the Great Wolf
Primarchs (series) part 2

At the the height of the Great Crusade, Leman Russ and his Dark Angel brother, Lion El'Jonson, come into conflict as they pacify the world of Dulan.
The Horus Heresy
novel

Also in:
Primarchs: the Audiobooks Volume 1
Primarchs: the Ebooks Volume 1