I found the book a challenging read in places, and an absolute joy in others. There seem to be a lot of long winded descriptions and musing on things that were barely relevant to the story, and didn't really add to the book at all.
The worst bit was book 3 - Notre Dame. Yawn. This description of Notre Dame, Paris and architecture droned on for 30 pages, and towards the end comes a sentence that made me laugh, it begins "Now if the enumeration of so many edifices, brief as we have tried to be..." Brief?? I just can't understand why the author felt the need to include these sections. Self indulgence perhaps, and an opportunity to discuss subjects that interested him, without giving much thought to the reader? I felt at times like I was rifling through a haystack that someone had dumped a chest of treasure over, searching for the gems amid the straw.
However, I'm glad I persevered, and I did find the second half of the book better than the first. What I loved about the book was the vibrant prose, and wonderful images. I found it to be humorous and light hearted in tone, in spite of the darkness of the story in many places.
I loved the initial description of quasimodo: "We shall not try to describe for the reader that tetrahedron nose, that horse-shoe mouth, the right eye which disappeared completely under an enoromous wart; those jagged teeth, with gaps here and there like the battlements of a fortress; ..."
I found wonderful imagery like this throughout the book, and I think that was one of the main things that made the book worthwhile for me. If only Victor Hugo had had a decent editor!