A MUGGY day in London town. I am walking through Bloomsbury on my way to meet the London-based, American writer Patrick Flanery. Why do I have the creepy sensation that I am being followed? Why this compulsion to keep turning around and looking over my shoulder? Am I being watched? Last night, on my way home, I thought I heard footsteps echoing mine. But why would anyone be interested in my every move?

After all, I am no one – just like the protagonist of Flanery’s superb new novel, his third. I Am No One is related by Jeremy O’Keefe, a 54-year-old Professor of Modern History and Politics, who it slowly emerges is not the most trustworthy of narrators. He specialises in German history and political thought; he’s also teaching a course on the cinema of surveillance at New York University (NYU) and has written a history of East Germans who worked as coerced informants for the Stasi – therefore he knows a great deal about the lives of others. Do others know a great deal about his life? Are they stealing his secrets and transgressions?

Recently returned to his native New York, which he left shortly after the 9/11 terrorist attacks, O'Keefe has spent a decade lecturing at Oxford University. In a Greenwich Village cafe, while waiting for a student who never turns up, he encounters, albeit briefly, a strange young man, who appears to know him. Soon, he’s convinced that he’s being watched, frequently seeing a black-clad figure outside his apartment building looking up at his window. He believes he’s being shadowed in the streets; then mysterious packages are delivered to his home. The gripping story takes devastating twists and turns as dramatic revelation follows piecemeal upon revelation.

It is impossible to read Flanery’s novel without constantly looking over your shoulder – if you can tear yourself away from the page, that is. This is such a superb, addictive, startling read that it seeps into your psyche. Read I Am No One and look around you with trepidation at our post-Edward Snowden world.

Neel Mukherjee, author of The Lives of Others, has garlanded I Am No One with advance praise: “A passionate, gripping, brilliantly voiced and scintillatingly intelligent novel about that cancer afflicting modern democratic states – the surveillance of its own people. Were we ever told that democracy would entail this? I Am No One will get under your skin, leave you jittery and unsettled...”

But then California-born, 40-year-old Flanery, who is charming and bookishly handsome, has a disturbing knack for unsettling readers. He did so with his critically acclaimed, South Africa-set debut novel, Absolution (2012), which won a raft of prizes and was shortlisted for another half dozen. At its heart is a legendary, Muriel Spark-ish writer and her biographer. Multi-layered, it deals with the aftermath of apartheid, historical crimes and collective guilt; it was translated into 11 languages.

His brilliant, state-of-the-nation second novel, Fallen Land, set in America’s mid-west, explores themes of dispossession, the pernicious effects of racism, cultures of surveillance and obsessions with security at all costs. Poet and critic John Burnside found it “an almost unbearably poignant thriller.”

When I tell Flanery how haunted I’ve felt since reading I Am No One and how I now keep looking behind me, he laughs delighted, disclosing that it all began one spring evening last year.

He was in New York and visiting a friend, a Professor at NYU, who lives in the university’s subsidised housing, the Silver Towers on Houston Street. “As I arrived, I looked up at the building. I saw my friend standing at her lighted window, I waved but she didn’t respond. I stood watching her until she moved away. When I told her I’d seen her and tried to attract her attention, she was astonished because although I could see her she had not seen me.”

Was she spooked? “Well, perhaps a little unsettled, although she’s yet to read the novel,” he replies. This incident set him thinking about how we have all become watchers and watched now that all aspects of our lives are monitored. “Once I had that image and the situation, I began thinking about how we change the way that we live now that we know what Snowden revealed. I think that writing the book was working through my own attitudes to privacy and surveillance, which shifted as I wrote. We all think there is too much surveillance but we are not going to be able to reverse what we have, so the question is how do we live differently without the expectation of privacy and what do we now demand?”

Within six months he had written I Am No One in the voice of a lonely academic, living alone in a featureless apartment in the Silver Towers, but whose private life may be about to become public.

Jeremy O’Keefe has certain characteristics in common with Nebraska-raised Flanery, who is also a Professor, teaching Creative Writing at Reading University. He left New York almost immediately after 9/11 to study at Oxford, in 2001, where he earned his PhD in 20th-Century English Literature (his dissertation was on adaptations of Evelyn Waugh’s novels), after studying Film at NYU’s Tisch School of the Arts. They both have Irish surnames. Jeremy, however, is a straight man – “And I am not!” exclaims Flanery, who shares his life with South African-born lecturer Andrew van der Vlies, with whom he’s been in a civil partnership since 2005.

When I mention the many resemblances, Flanery says: “Each of my books plays with biography and autobiography. In some ways, this book is pushing that play farthest. I suppose it’s a kind of tease to the reader who wants to read fiction biographically but, in other ways, it is almost a working through, also like a psychological [working through]. But I am not like Jeremy at all.”

That’s a relief, I tell him because Jeremy is not that likeable. “Exactly! That’s what I wanted – the book asks how we feel empathy for people who do not inspire empathy originally and who continue to be distancing. He does all sorts of things to distance himself from other people. The core characteristics that he and I share are displacement and that experience of migration and acculturation. As an American living abroad, that is something I try to engage with in all my work and try to understand, along with my shifting attitude to it, and the feelings of loss that I still have as a result of migrating to England, but also the benefits, too.

“The loss? Oh, the feeling of having a natural home, of belonging somewhere, because now I don’t belong anywhere. Andrew feels that, too, but not when he returns to South Africa. I think his experiences aren’t as acute as mine because as an English-accented South African he can pass as British. Whereas, when I open my mouth I am immediately noticed. Even though when I go back to the States they say I sound ‘terribly British.’ There are times in London when I can ‘pass’, but they are few. That kind of experience is one I continue to be really interested in.

“There are more profound complications – if one lives outside one’s country one fears becoming suspect at home. I write about Jeremy’s difficulties in having an Irish name in England. That is something I have experienced – in Oxford and in Sheffield, where I taught at the university. I would go into a shop, have a perfectly nice conversation with someone until they saw my name on the debit card and it was like a curtain had fallen. Total ice! I understand that response but I feel saddened by it.

“They are making an assumption about a surname, knowing nothing of my background or the fact that I was not raised a Catholic and am in fact an atheist. It is also about the deep association that people attach to names – something I engage with in the book.” (When a woman called Fadia is mentioned, Jeremy’s ex-wife sneers, “Fadia? What kind of name is that? Are they Arabs?”)

Which leads us to a discussion of the American political landscape – we met shortly after Donald Trump’s call for a ban on all Muslims travelling to the USA. “The spectre of a suddenly Fascist America that Trump seems to represent is totally terrifying,” sighs Flanery.

The only child of liberal, left-leaning parents, he recalls political debates beings dished up at the family dinner table. He's been quoted saying that he recalls feeling depressed about Ronald Reagan’s election in 1980. “Yes, I was. I was five-years-old, but I remember the sadness, the defeat.”

Flanery’s first job in New York was working as a Hollywood literary scout – he read the best of contemporary fiction and assessed it for possible film adaptation. Would he have recommended I Am No One? He can’t stop laughing, then says: “If I really loved a book, I would say, ‘This would make a great movie.’ So, yeah, to Hollywood, ‘This would make a terrific movie!’”

You know something? He’s right.

I Am No One, by Patrick Flanery is published by Atlantic Books, priced £12.99.