When I started reading this story, I wasn't enjoying it. It felt too "rich people with ennui" to me. It substantially improved and the sudden weirdness/fantasy at the end was great. There is some subtle foreshadowing of the weirdness early on, I think.
Link for those who want to read it:
Someday we're going to have to do Viriconium. But not until 2030 or so when we will have just finished The Book of the New Sun.