Some of the reviews I have read of this novel seem to me to miss the point badly. Readers who complain of confusion were looking for a single protagonist whose storyline they could follow, but the protagonist is London in 2016/17, and that can only be brought alive through a multitude of characters whose lives constantly intersect, merge and diverge.
The body of a woman, fished out of the Thames, cannot be identified, though indications are that she was a suicide. Two men, Pete, the policeman who worked on her case, and Alan, who makes a TV documentary about it, become invested in finding out more about her (in Pete's case obsessively) and the story mainly follows them, their ramifying families and friends and the neighbours Alan and his wife Francesca encounter in the district of London to which they have just moved. The word "stranger" in the title might lead one to expect a focus on isolation, on lack of connectedness in the big city, but this is not so. The characters actually interconnect in a lot of ways, some of which they are unaware of, and the London built up in the novel is one of neighbourhoods, separate, sometimes seeming alien to each other, but still crossing and interacting.
Most of the characters, though, either first arrived in London as strangers or have parents or grandparents who did so. The ethnic diversity of London is constantly stressed, and one theme which emerges very strongly is the way in which, after the 2016 referendum and the 2017 London Bridge attack, people who had long felt at home there began to sense hostility from their neighbours. It is in this sense that the city, rather than those in it, begins to become a "stranger".
This creeping unease is well conveyed, though it is possible to wonder if it might be overdone. That one of our characters might suffer a race-related attack is credible; when the tally gets to three, I do wonder if it still is. Though, not being a Londoner, I have no way of knowing for sure. I don't know, either, if the description of the deportation trains is accurate:
With the thaw, Alan spent even more time sitting alone at the end of the garden, his ear cocked for the thrumming on the rails of the occasional deportation trains diverted along their branch line, the filthy engines spattered with mud coming down from the north-east. The carriage windows were blacked out, desperate fingers scratched away at the paint. […] Rows of human monitors along the track held up placards of protest and solidarity. Most days he joined them on the bridge.
Inside the trains the deportees raised their palms, pleading at the glass. The deportation infrastructure formed a network of cross-hatching across the eternal landscape of England, its woods and remaining patches of forest, its indigenous trees and its invaders, oaks, rills, brooks, ditches, barrows, mountains, faint vestiges of enclosed commons. Across all this, solid lines of track were moving towards temporary detention centres and on to airports and sea ferries.
Some readers' reviews have dismissed this as exaggeration, an attempt to invoke the Holocaust. To me it sounds likely, though as I say I can't know for sure. In a way, this is the point: that this issue fractures society to the point where some will find it eyebrow-raising but credible, while others will dismiss it out of hand. Pete and his wife Marie have this argument at one point:
If you lived in a coastal port, you had to expect people would come in as well as go out. Some of them would be bad 'uns. He'd tried to explain that to Marie. You couldn't have London without foreigners, it wouldn't be the same place, would it? It'd be some lily-white National Trust mock-up with volunteers dressed in mob caps and packets of shortbread in the gift shop.
Actually of course it could be something a whole lot worse. Francesca at one point stumbles on an enclave known as "the Island", though it isn't one, which has managed to insulate itself from most of the change around it. It is an inward-looking community, hostile to outsiders, mostly ageing; the only two children in evidence show signs of mental incapacity. Anyone with any get up and go has long since got up and gone. The message is clear: communities that resist change and outside influence do not just stay the same, they stagnate and turn sour.
The denouement of the body-in-the-Thames thread doesn't feel quite right to me; I could have wished for more mystery to remain. And I did, sometimes, lose track of the myriad characters and think "who the hell was Johanna?". Hint to litfic writers: genre authors sometimes give readers, at the start, a list of characters with identifiers ("Johanna, Alan's work colleague"). It isn't the worst idea.
These are minor points about a novel as pulsing, colourful and alive as the city that is its protagonist. I enjoyed it greatly, and I'm not even a fan of London.