The Collected Visions books were largely based on a trading card game, and incorporated older (but great, in my humble opinion) concept artwork by John Blanche.
The new books collect the covers of the Horus Heresy series, as well as other, newer illustrations. I'm guessing older artwork is recycled, as well - but that's conjecture on my part. I would also imagine that, like the Collected Visions books, this will also serve as a primer/summary of the events shown in the novels, novellas, short stories, etc., thus far.
Last edited by Phoebus; 02-01-14 at 01:58 AM.