Cambridge's prose muddles mental states together ordinarily, in the cocktail sense. Such is the normal condition of her people.
It is a subtle effect and understated-complex but I think her books are easy to dismiss because she sounds so cuddly (most of the literature-overviews I've read either ignore her or give her a pat on the head); her language is friendly but the events are often terrifying (which makes her even happier; she's entertained when she's narrating a railway accident in A Marriage Ceremony, "most of them screamed horribly"), and at the end of Sisters I see how, with only a slight change of tone, she'd sound nihilistic.
She loves to set people up as if they're going to be around for the rest of the book and then knock them off like Hitchcock. She spends a chapter describing a woman meeting her fiancé, marrying him, having a baby, "with the bloom of that most beautifying convalescence like a halo about her," looking forward to her new life in a fresh house, getting in a boat for the first trip to the new house, everything innocent with anticipation, "her contented eyes shining like stars," and then there is a long period of pausing in which you know someone is dead or about to die, and it is her. A Humble Enterprise has to start by killing a deaf man with a train.
Joseph Liddon was deaf, and one day, when he was having a holiday in the country, he crossed a curving railway line, and a train, sweeping round the corner when he was looking another way, swept him out of existence. On his shoulder he was carrying the infrequent and delightful gun -- reminiscent of happy days in English coverts and stubble fields -- and in his hand he held a dangling hare, about the cooking of which he was dreaming pleasantly, wondering whether his wife would have it jugged or baked. When they stopped the train and gathered him up, he was as dead as the hare, dissolved into mere formless tatters, and his women-folk were not allowed to see him afterwards.
Such gaity in "mere formless tatters," such a light and happy sound. Mere! formless! tatters! "Mere" goes out when the mouth stretches into a smile on the e, and "tatters" jiggles around on tt-tt-rr. She mixes cocktails even in the language like this: the most terrible things are reported as if they are maybe a bit normally unfortunate though also admittedly terminal. The thoughts she is having about the mutilated human are defiant of death and stillness; they are energetic thoughts, and she is not ignorant of the equilibrium that has been formed between the man and the hare. The difference between them (formerly so striking, "he held a dangling hare" and the mechanism of death to him is "delightful") has been removed with the aid of an as: "as dead as the hare." The hare died recently, now the man who killed it is dead, and death will extend over the entire earth; the driver of the train will die eventually, and so will the womenfolk until they're all as one another, death coming with a smooth swish-swish ("sweeping," "swept") and the formalities of the living going on after they have passed into darkness, all the laws, and officialments and paternalistic decision-making still puttering on in a mechanical way with their predictable manners -- "not allowed to see him afterwards" -- all the physical laws of the universe trundling ruthlessly, the train that killed you still needing to stop before the people on board can come down to pick up your corpse.
Question: what is her subject matter? What does she come back to? Answer: the intractability of the material universe. That's why she has to keep muddling things together. Not as if conscious and planning, but as if brought to it.