Hannes just shared on facebook that his book is out now (Hal Leonard books).
It's 112 pages (softcover) & CD, $19.99.
Here's some more info that I've copied from that link.
Extreme Metal Drumming
Exteme Metal Drumming
is your guide to an exciting musical genre that features great technicality, fast and complex double-bass patterns, odd time signatures, erratic song structures, and blazing tempos. This logical, step-by-step approach will enable drummers to acquire the diverse skills needed for this style while emphasizing musical applications of the techniques. Includes a foreword by George Kollias.