Doomscream points us to the website of book publisher Insight Editions, where can be found readable (zoom in and scroll around) versions of the previously-seen sample pages from the Book of Cain. There are 9 such pages, though they are unfortunately not contiguous, aside from the first two.
Still, you can get a nice sense of the book’s style and content, plus read the foundational myth of the entire universe; apparently the seven greater/lesser evils came from the seven heads of a primordial dragon of evil? (Just like my ex-wives.)
Elsewhere, BlizzPlanet has info on many of the contributing artists, plus a few additional promotional images obtained from the publisher at their NY Comic Con booth. The pictures are kind of flash-blinded, but are still worth a look.