I don't remember who recommended this book - it may just have been the New York Times - but it wasn't really the type of book I normally read. If I had known more about the story I probably would not have read it, but the story would be significantly worse if I had known it in advance so I will also not give away much of the plot.
Though the book is not my normal type, I was sucked into the narrative and stuck with it for the almost 600 pages it took to tell the story (though it could have been told in about half that number). The style is formal, old fashioned English - that is part of what I did not really like about it. The plot was in fact quite racy - and I'm sure would have been considered much more so in 1922 when the story is told. So the formal language didn't quite fit - though I suppose that juxtaposition may have been part of the author's point. Sort of - "see what's hidden behind all those upper crust manners".
Mrs. Wray and her daughter Frances have come upon hard times. Both of Frances' brothers were killed in World War I and her father dies shortly after, leaving them with a crumbling though fashionable home and a burden of debts. During the war we learn that Frances lived in town rather than the suburbs and dreamed of a very different life. However she abandons all of that to take care of her mother and her home (much to her mother's shame they cannot afford servants and Frances must do the housework on her own though she tries to conceal this from her friends as best she can). In order to supplement their income, the Wrays take in borders - though this is also a humiliation for Mrs. Wray so they refer to them as "paying guests". Frances shudders the first time she must suffer the embarrassment of taking payment.
The borders are a young married couple, Mr. and Mrs. Barber. They are from the "clerk class" and introduce music, laughter and "bordello like" decor into the home. To Frances they also appear to be very unhappy. She gets closer to the couple than her mother would like - and that is where the story gets mysterious. As I said, I do not want to give anything away, suffice it to say she develops a very complicated (and somewhat unexpected) relationship with the couple, they get themselves into some trouble and the remaining hundreds of pages deal with how that trouble resolves itself.