The series of books are called "PzKpfw IV at the front" primarily because most images are taken by the troops themselves.
Volume 3 covers Ausf F, Ausf F2(G) and early Ausf Gs. The reason for publishing this volume first is this hectic period of change of role and use; from short barrel to long barrel is of most interest to me and has been the main initial focus for my photo collecting.
Volume 4 continues on to mid and late Ausf G, Ausf H and Ausf J. Taking the story to the end of the war and onto post war use.
The subsequent volumes will prequel these adding imagery from early and pre war use right up to the invasion of Russia and the fighting in North Africa.