The first part had the loveliest off-hand turns of phrase that would make me pause to savor them for a few moments. Also a lot of rather quotable philosophizing about the nature of desire and mortality, etc.
Then after he moves in with Lucy, everything turns ugly. It lacks a sense of redemption, which I was looking for, and needed, hence the depressing feeling at the end. I'm sure there's more to it going on, something about the Byron opera and the parallels between the adultery and the rape, but I don't want to think about it any more. Like a few other reviewers, I'm off to find something light and uplifting as an antidote.