With the assumption that you've read the first book:
It's a few months after the events of Garnethill. Maureen has a new job, working for the same organization that runs the battered women's shelter where Leslie works.
She's miserable. Her family is still a disaster. As her father is still in town, she won't see them anyway, but it would maybe be nice if they didn't treat him as the prodigal son. Her friendship with Leslie is falling apart. She's seeing someone but it isn't working out. She's still being badgered by the police and has been receiving threatening letters:
She picked it up and went back into the kitchen, sat down and lit a fresh cigarette from the dying tip of the old one. The envelope was made of cheap porous paper, her name and address written in a careful hand. She leaned across to the bills drawer and pulled out the pile of blue envelopes, laying all fifteen in chronological rows on the table. The writing was changing, becoming more controlled. He was getting better. Some of his letters were threatening, mostly they were gibberish, but the threats and the gibberish were evenly interspersed, regular and anticipatable. She knew the voice of random insanity from her own time in mental hospital and this wasn't it. He was a rapist and a murderer, but she wasn't afraid of him and she didn't give a shit. He was locked away in the state mental hospital. It was like being challenged to a dancing competition by a brick.
When one of the women from the shelter turns up in London, very very very dead, Maureen sees the situation as an escape from her problems. She heads to London to investigate the circumstances of Ann's death.
This is going to sound strange, but my reaction to this book was similar to my reaction to the most recent Harry Potter book.
Exile has the same fantabulous writing as Garnethill, the same realer-than-real characters and the same amazing sense of atmosphere. But the plot felt like it was mostly just there to get everything in place for the last book in the trilogy. Then again, the same can be said of Empire Strikes Back.
I read the book in one sitting, found it totally engrossing, and enjoyed it. But it did end up feeling very much like a set-up for Resolution. Which I guess isn't really a complaint -- because I can't wait to read it.