It is, obviously, about the old man that is Malcador. It is written by Chris Wraight and you can pre-order it off Amazon
Here is the cover art:
Long has Malcador stood at the Emperor's side - as confidant, aide and ambassador. Now learn the truths of his mysterious past, kept secret since the glorious wars of Unification.
Look at the numbers on the skulls. Spooky.....