I found a link to this in a google alert late last night. Phantom Of The Opera - Unmasking The Masterpiece (2013) http://www.preservehollywood.org/DungeonWebNew/Home.html
According to the website this is a comprehensive look at Phantom in all of its incarnations; movies, books, plays and of course the Webber musical. Even Elissa's favorite Phantom, Hugh Panaro weighs in! I have ordered my copy and will let you know what I think of it. It only has 5 reviews on amazon, but all of them are 5 star, so this bodes well.
Editorial Review from amazon
"Phantom Of The Opera - Unmasking The Masterpi