Okay, I’ve finished it. And, inexplicably for me (I don’t generally like long, overly wordy books), I loved it. I guess it’s kind of like one of the messages in the book itself: you can’t necessarily pick what speaks to you, or what you like.
I agree that it probably could have been quite a bit shorter, but even so, it worked for me.
Finished it last night. Hated it to the very last word.
Dear Infovore,
I can not thank you enough for this post. When I read your post I put my name on the list for the book at my library. It was finally available Friday and I just finished it. What a wonderful book. Beautiful writing. Thank you thank you thank you:)
Thanks! Glad to be of help! 
ThelmaLou, why did you hate it? I admit I had a totally different ending in my head–the painting would be destroyed/lost, Theo would be out from under its spell (cuz it’s a horcrux), and he and Pippa(?) (the red-headed girl) would marry and live happily ever after. At the end I could not stand Theo. He was such a whiny bra who cheated the man who gave him his only sense of family. At least Boris was honest about who and what he was. And for the author to have a blanket explanation of how Boris got the painting ("you black out when you’re drunk) was a total cop-out.
Read this on holiday. Really loved it. I cried at the last page - this is very unusual for me! I read this thread prior to going away and so was expecting this overly verbose, unending book but it was far from that for me. It was by no means lean, but in order to cover that time, and the arc of the lives - i thought it worked fine. Were i not on holiday I suspect I might have taken months to finish and that would have been a completely different experience. It reminded me of Robertson Davies’ Deptford Trilogy - which is a very high bar imho.
I work in adolescent mental health and thought the link between trauma and addictive behaviours was really skilfully handled.
I’m very glad I’ve read it and have recommended it roundly.
MiM