This book covers the early version of the Sturmpanzer IV Brummbär known for the multi-angle casemate design and direct vision slot for the driver among other things. Because it is Volume One, I would think (hope) that there are more volumes on the way covering the mid and later production types.
While Kagero's Photosniper book on the Brummbär covers all three versions, has more color detail photos, line drawings and bonus decals, this volume is wonderful because of its field deployment photos. I don't think I've ever seen such a collection of "in action" shots of the Brummbär before. Lots of diorama potential here! It also contains crisp line drawings that even show the "Continental" lettering on the road wheels and return rollers.
If you're a fan of this building-smashing machine or Panzer IV variants in general (and who isn't?), you can't go wrong.