“Mrs Osmond is both a remarkable novel in its own right and a superb pastiche,”
says Edmund White in The Guardian.
https://www.theguardian.com/books/2017/oct/14/mrs-osmond-john-banville-review
“Mrs Osmond is competent, safe and reliably dull,”
says Adrian McKinty in The Australian.
McKinty wonders about Banville’s sudden interest in writing pastiches:
“His previous effort, The Black-Eyed Blonde, was a journeyman sequel to Raymond Chandler’s The Long Goodbye…”
and concludes:
“We can only hope that something exciting happens to him in real life or else, no doubt, a dishevelled, rosy-cheeked Molly Bloom shall arise from her linen sheets and be coming soon to a bookshop near you in a quality hardback edition.”
http://adrianmckinty.blogspot.com.au/2017/11/john-banvilles-mrs-osmond.html
It does seem strange that Banville, who has said The Portrait Of A Lady is the most perfect example of the novel form in English, should feel the need to write a sequel. Has his fame gone to his head? We know he does have a very high opinion of his own style – when The Sea won the Booker he said he was pleased that “a work of art” had won. Or, assuming that he might have a sense of humour, is it possible that he’s playing games with us now that he can, as McKinty says, publish anything he wants these days? Is he just seeing what he can get away with? All that stuff about how skinny Osmond’s legs are – and as for what he does with Pansy!
Gert Loveday's Fun with Books 
who knows. I have a friend who was a Banville fan who has given up on him.
I read The Sea years ago and found it very dull.
The one after The Sea, I forget its name, was on the same theme. He seems to have run out of ideas. Maybe that’s why the pastiches.
With a recommendation like that, I think I’ll give it a pass.
Leslie
There are lots of things more worth your reading time. The other Gert is very cross because she actually bought the book!
Books can be very costly. One does like to select the best to read. (Our time is rather precious too)
Leslie