Horus Rising by Dan Abnett

This is the launch title in an amazing new series that tells the incredible story of the Horus Heresy, the civil war that almost tore the Warhammer 40,000 universe apart. Penned by the Black Library's best-selling authors, the Horus Heresy range will pull no punches, dealing with classic themes of honour, duty and betrayal in a unique SF setting. After thousands of years of expansion and conquest, the human Imperium is at its height. His dream for humanity accomplished, the Emperor hands over the reins of power to his Warmaster, Horus, and heads back to Terra. But is Horus strong enough to control his fellow commanders and continue the Emperor's grand design, or will such incredible power corrupt him?