I've just finished it and really really enjoyed it. Middlemarch came to my mind too - obviously she's no George Eliot but the book has that ambition. I counted 16 major characters, whose lives are all intertwined very cleverly.
Thinking about it, I was also put in mind of Dickens - she has that same moral anger about the way the well-off wash their hands of responsibility for the poor. She does manage to make that moral anger more palatable by portraying some of those characters, such as the Mollisons, in broadly comic terms.
I was also interested in the way that there is one good man, Barry Fairbrother, whose goodness continues to highlight the moral failings of the other characters throughout the book. All the good he's done unravels. And there's the irony of the spiteful "ghost of Barry Fairbrother" messages, which are the exact opposite of his own approach, which was one of reconciliation and kindness. The ending is hugely bleak, much more so than I was expecting. (Someone on Amazon pointed out the similarity to the parable of The Good Samaritan, which is true - it's not the churchgoers who do the right thing at the end, but someone from the "wrong" religion.)
It's funny how literary critics always complain that there aren't any novelists writing state-of-the-nation novels, but when one does, they mostly hate it.