"Nobody's Wife" by Laura Pearson

An audio book.

In the prologue the first person PoV says that one of Josephine (the half-sister she used to share a flat with, 3 years her junior), Michael (husband who's never really excited her) and Jack (Josephine's boyfriend) has died. She wants to say sorry. These 4 characters take turn at having the point-of-view. They live in London.

Michael met Emily when she was 24 and he was several years older. After years (she was unsure?) they got married. Jo was around too much for Michael's liking. Emily never knew her father and her mother was in Australia with a man.

Jo had asked Jack out (he worked in a bookshop and was a budding writer). He'd become bored with one-night stands. Jack's mother had remarried to a man Jack didn't like. Jo soon falls in love. Jo (a piano teacher) wants Emily to like Jack, who has scars on his chest and back.

Ben, about Emily's age, had moved next door when they were all little. He's like a big brother. Jo's father makes contact out of the blue after decades.

After Emily and Michael return from their honeymoon (going by train around Italy) they move into the house Jo and Emily grew up in. As soon as Emily and Jack meet they're attracted. Emily thinks about being unfaithful. Jack and Emily (a teacher) both risk taking time off work to meet for the first time, not conversing online first. Both are disinhibited though Emily’s only been married a few weeks, and Jack’s girlfriend is Emily’s sister!

After a few weeks of marriage Michael wants to go to Leeds for 3 weeks to stay with his parents and do research for his next novel. He thinks this idea is feasible (really?). Emily doesn’t express surprise (really?). He could have gone just for weekends, he could have waited until the school holidays. His parents could have lived in India. While he’s there he reads Jack’s short stories and is moved to tears by their sadness. Meanwhile Jack who has “eyes like heavy clouds” sleeps with Emily frequently. He hasn’t shown Jo or Emily his stories. He tells Emily (but not Jo) that his scars were caused by his step-father’s belt.

Emily becomes pregnant (why were she and Jack so careless?) just as Michael suggests they should start a family. She doesn’t know who the father is so has an abortion. This has happened to Jack before. She thinks about ending the affair.

Jo discovers Emily and Jack in bed and spills the beans. Emily splits with Jack. Michael goes to his parents without telling them why. Jack writes a short story about Emily. Michael’s completed (and accepted) 2nd novel is about Emily. Jo has a long discission about divorce with her long-lost father. Michael dies in a car crash, no other vehicle involved. The wake seems to start a reconciliation between the sisters.

Several sentences start with "Later".