Well if any entertainer deserves a multi-volume biography, it's Bing Crosby. You could break his career down into several topics and write a book on each of them. It was unparalleled really.
As for opinions, yes the author has opinions, but there are an awful lot of (non-extraneous) facts as well. And the opinions are of the highest caliber- he's a well-respected jazz critic and is also extremely knowledgeable about the era, its movies and its culture generally.
Part one is an essential and definitive biography, and I have no reason to doubt that the other two parts won't be as excelle