This book is an essential guide for anyone who wants to command Mechanicum armies in Warhammer: The Horus Heresy. It contains the rules you need to field the various deadly and esoteric machines and troops of the Taghmata Omnissiah, whether they are loyal to the Emperor or the Warmaster. It includes Detachments, Wargear, and special rules which make the Mechanicum a unique force on the tabletop.
This 152-page hardback book contains:

Background and lore: Information on the Mechanicum, their organisation, and examples of their forces.
Rules and unit profiles: A guide to army building, plus rules for units, weapons, and Wargear available to the Mechanicum in Warhammer: The Horus Heresy.
High Tech Arcana: Rules and Detachments for the following faction traits: Archimandrite, Cybernetica, Lacrymaerta, Myrmidax, Reductor, Malagra, and Macrotek.
Cybertheurgic Rites: Additional rules that reflect the esoteric ways in which the Mechanicum does battle.
Machina Malefica: Unit profiles for creations infused with the dark energies of the Warp.
Visual showcase: Colour schemes for infantry and vehicles, and a gallery of stunning miniatures photography for the Mechanicum.

You will need a copy of Warhammer: The Horus HeresyAge of Darkness Rulebook, available separately, to use the contents of this book.