This is probably the most recommended book by the historians I know in the 82nd Airborne Association. Marshall's unique position allowed him to write an authoritative account of the Paratroopers operations in Normandy.
This reads like it was taken from his offical military records, so there is detail. The first part of the book is the 82nd, and the second part is the 101st.
his drawings and maps are very specific to the local actions of specific units. And they are not great, since they are basically hand sketches. ( again probably taken from his orginal reports, though this is just a guess on my part ). So you will get the detail, but you really need to have a basic understanding of the entire operation to really appreciate and follow his accounts. (this is not a con, just an fyi ).
The other major point with this book is that it is not taken from veteran accounts decades after the war. So this is 100% fact from his work during the war.
All The Way!