The Horus Heresy Book One - Betrayal is a supplement for Warhammer 40,000 dealing with war and battle in the dark age of the Horus Heresy. This book, lavishly illustrated in full colour, contains extensive background information on the Imperium as it stood at the end of the Great Crusade. Also detailed are the histories of the four Legions who took part: the Sons of Horus, Emperor's Children, World Eaters and Death Guard and an extensive campaign system. This book also contains a complete Space Marine Legion Crusade Army list as well as games rules for the Primarchs of the four Legions, super-heavy vehicles and special characters featured in the story.

The third and final part of the Isstvan trilogy. This book details the aftermath of the Isstvan V Dropsite Massacre, and two other major battles fought between the Loyalist and Traitor Legions as the Horus Heresy swept out from the Isstvan system and into the wider Imperium of Mankind: the Battle of Phall and the Invasion of Paramar. Also featured are the background and game rules for the four Legions covered in this book: the Alpha Legion, Imperial Fists, Raven Guard and Iron Warriors, and a Mechanicum army list, plus new campaigns and vehicles. This lavishly illustrated, full colour, 285 page hard cover book is leather bound with metal corner clasps stamped with the Imperial Aquila, and features a red ribbon bookmark and foil-edged pages as well as an embossed cover and spine.