Available now is Age of Darkness Rulebook for the Horus Heresy from Forgeworld
Here is a direct link to the new book (as its not yet listed under new releases)
https://www.forgeworld.co.uk/en-EU/The-Horus-heresy-Age-of-Darkness-Rulebook-2017
via Forgeworld on the Warhammer Community
https://www.warhammer-community.com/2017/12/25/now-available-horus-heresy-age-darkness-rulebook/
Excellent news, Horus Heresy fans – we’re very happy to announce that the Horus Heresy: Age of Darkness Rulebook is now available to order from Forge World.
The Age of Darkness Rulebook is the essential reference guide for every gamer in the 31st Millennium. Inside, you’ll find the same great rules you know and love from the previous edition of Warhammer 40,000, meaning all the Horus Heresy books you already own are still valid, while material from the latest round of FAQs has been added to the game in order to make bookkeeping that bit easier. You’ll also find handy reference material, like universal special rules unique to the Horus Heresy, and weapon profiles for Age of Darkness wargear like volkite weaponry.
The Age of Darkness Rulebook can be ordered from Forge World – check it out (and don’t miss your chance to claim a free shipping voucher) today.