A curious read. Unlike many other people who have seen the musical, I knew that the story contained within the book bore little resemblance to the one on the stage. 
 I expect having seen the musical impacted on my enjoyment of the book. Not so much in that I disliked the differences, but I was distracted by continually asking myself what parts of the book remained intact. I probably would have enjoyed it more of I'd read it when I first bought the book, rather than over a decade later. :-) 
 If you approach it like a standard fantasy novel, then you'll get more enjoyment out of it than by thinking of the story it was influenced by, and the one it went on to inspire. 
 My only criticism was that it really needed so decent editing.