Early in the book, Edsel details how art experts throughout the allied countries secured and protected their art treasures in anticipation of military attack by the axis powers. This included hiding many of them in remote areas, often in climate controlled bunkers. This is something which I never really gave much thought to before: the necessity of keeping cultural treasures safe from destruction during wartime, especially in Britain, which was being routinely bombed by the Nazis. This also reminded me of when, hiking in the Scottish highlands, I passed by a bunker built into/under a hill. Reading later in a guide book I found out that it was used to store gasoline during W.W. II, hidden away a corner of the Scottish wilderness to keep it safe from the Blitz. This is essentially what was done with art treasures as well.
One great difficulty which the MFAA found themselves dealing with was the near impossibilty of finding information about where the Germans had hidden a lot of their pilfered prizes. Many of the towns they entered were bombed-out wrecks, the buildings which had contained the German's records destroyed. In many cases, the Germans had destroyed the papers themselves, to hide their tracks.
In 2014, George Clooney made a movie called The Monuments Men which was loosely based on this book. It didn't do well despite having a stellar cast. I didn't see it, so can't comment on why but suspect that it might have something to do with the difficulties in turning a non-fiction book into a fictional movie.