This volume (actually "Volume IV" consists of two volumes, Volume IV/1 and Volume IV/2) is an incredibly detailed and dense look at a huge range of issues relating to the German invasion of Russia in 1941, running to almost 1500 pages.
Of this page total, however, "only" about 500 pages are devoted to the military campaign. The remaining pages go into great detail on other aspects of the war, such as planning, economic, diplomatic. etc, including lengthy chapters on topics such as "The Involvment of Scandanavia in the Plans for Barbarossa", "Operation Barbarossa as a War of Conquest and Annihilation", etc. The book includes an incredible amount detail on a wide range of topics, but is also a very slow read.
On the downside, I have seen better treatment of the military campaign itself, and the fact that these volumes were in fact written by several different authors means that sometimes it is not completely consistent. For instance, at least one of the authors seems to blame the German atrocities in Russia on the Russians ("They started it...").
In conclusion, for someone interested mainly in an account of Barbarossa military campaign, I would recommend Glantz, Luther, or Ericksson over this book, but if you are very interested in economic and diplomatic aspects of the war (at least on the German side), this might be the book for you.