The Codex Astartes details the doctrine of the Space Marine Chapters, compiled and written by the Primarch of the Ultramarines, Roboute Guilliman. While not every Chapter follows the Codex completely, it lays the foundation for their organisation and tactics.
About this series:
The Adeptus Astartes are genetically engineered warriors, created by the Emperor of Mankind and tempered by centuries of bloody warfare. The Index Astartes series explores in detail the many elements of the Space Marines armies on and off the battlefield, from the newly inducted Scouts to the vast battle-barges that carry them to war.