If your a fan of the Horus Heresy series and in particular the fantastic work of Aaron-Dembski Bowden by far the best author in the series then you will, like me, be a huge fan of the Word Bearers the only Astartes to hold to the true faith.
[Skip the next bit if you haven't read the books First Heretic & Betrayer as there are spoilers here]
Of the various novels that discuss the Word Bearers, and their righteous ascent from the Imperiums corrupt belief in the false god emperor, the character of Argel Tal and the blessed members of the Gal Vorbak stand out. I've read the novels 'First Heretic' and 'Betrayer' I don't know how many times now but enough for my copy of First Heretic to start looking seriously battered. In these the depiction of Argel Tal's changing belief structure and his internal struggle to absorb and live with the changes he himself, his Primarch and the Word Bearers legion must undergo is a strong central theme. His betrayal at the hands of Erebus the man who brought him into the Legion from his home on Colchis is a pivotal moment in this story. More pivotal though is the journey of Argel Tal and his company into the Great Eye, their eventual return and then ascent to saint hood and transformation into the Gal Vorbak upon the battlefield of Istvaan V.
While I have put my 30k project on hold and have no real interest in taking up 40k as a game I am still very interested in collecting the Horus Heresy models produced by Forgeworld. Despite an early rush of Word Bearers related products they diverted into the other legions for a while but have finally come back with the models I have been waiting for - the Gal Vorbak. And they look awesome....