Yes, it's an important book for many reasons.  It's extremely well-researched and annotated almost to the point of tedium -- except, of course, that the documentation is essential for credibility.  We need a similar book to give us a fuller picture than we have now about Pope Pius XII.  Pope Francis should act immediately to make all of the relevant archival material available to historians and researchers.
The religious leaders of our day, especially in the United States, would do well to remember that a future generation of historians will study the resurgence of Nazism, fascism and racism under Donald Trump. A good exercise for them would be to write the chapter they hope will be written about them.  History will ask: Where were you, what did you say and do, to stand against the reemergence of fascism?