This book is very slim, even by Ospey standards - 47 pages of large font type somehow slipped between lots of pictures and tabels. But the pictures are mostly small and don't show a lot of detail for modelers. The color plates are paintings of four side views, one 3-view, one 3/4 external, and one 3/4 cutaway of Stug IIIs, and one 3-view of the Stug IV (with schurzen - not helpful!) and a corner view of a Sturmhaubitze. There are some schematic drawings, but they are at 1/76th scale which is not very useful because it is both very small, and of a not commonly used scale for modeling (1/72 would be good, 1/35 would be better). There is only a single paragraph on Stug IVs total.
It is a decent overview of the vehicle, how it is used and its strengths and weaknesses. But it isn't really helpful for people making models or looking for more than just basic information.