One of my all-time favourite books, I really do think it's quite perfect. Have been re-reading it recently.
It is quite similar to Brideshead Revisited, isn't it? The Oxford connection, the protagonist's obsession with the aristocracy and beautiful things/people, the fact that Nick/Charles are both charged with 'looking after' Sebastian/Catherine and then used as scapegoats for their behaviour. But The Line of Beauty completely stands apart as its own book, and is very much about Thatcherism and the 80s etc.
The Marchmains are more attractive personalities than the Feddens, though - I want to punch Gerald in the teeth even though he is a fictional character.
Also, does Nick have AIDS at the end or not? I thought he did, because Wani did and Leo, but then he says he has already had one test which was alright and he is having another, and this is after he has stopped sleeping with Wani.