I'm seeing several recommendations for the thriller Ordinary Thunderstorms by William Boyd.
About the book:
One May evening in London, Adam Kindred, a young climatologist in town for a job interview, is feeling good about the future as he sits down for a meal at a little Italian bistro. He strikes up a conversation with a solitary diner at the next table, who leaves soon afterward. With horrifying speed, this chance encounter leads to a series of malign accidents, through which Adam loses everything—home, family, friends, job, reputation, passport, credit cards, cell phone—never to get them back.
The police are searching for him. There is a reward for his capture. A hired killer is stalking him. He is alone and anonymous in a huge, pitiless modern city. Adam has nowhere to go but down—underground. He decides to join that vast army of the disappeared and the missing who throng London’s lowest levels as he tries to figure out what to do with his life and struggles to understand the forces that have made it unravel so spectacularly. Adam's quest will take him all along the river Thames, from affluent Chelsea to the gritty East End, and on the way he will encounter all manner of London's denizens—aristocrats, prostitutes, evangelists, and policewomen—and version after new version of himself.