Horus Heresy, a two person board that allows players to play out one of the seminal moments in the 40K mythos history.
I'm not sure how different this new release is when compared to the 1993 release. However, I think it's safe to say that it will be fun. Whether you care or not, in the fluff few events are more important to the 40K universe than the Horus Heresy. So I doubt Games Workshop would do anything to detract from the popularity (and money making potential) of this story with a poor game. (Courtesy Bell of Lost Souls)