The skitarii are the soldiers of the Machine God, the tireless legions of the Adeptus Mechanicus. Holy warriors, they carry the word of the Omnissiah across the galaxy, destroying the impure machines of aliens and renegades and spearheading the Quest for Knowledge. A discovery of ancient technology sends a skitarii legion, commanded by Alpha Primus Haldron-44 Stroika, into battle on a forge world overrun by Chaos. When a cataclysm cuts him off from his tech-priest overseers, Stroika must rally his forces and battle corrupt machines and Chaos Space Marines if he is to achieve victory.

Read it because
This is a fantastic insight into the inner workings of the Adeptus Mechanicus, and a display of their resilience in the face of absolute disaster. Plus, cold, unfeeling cybernetic efficiency in battle against the merciless swirl of Chaos is always a recipe for action.