"I'm so self-indulgent as a writer that this question of who is going to read the book never occurs to me," says Dyer, who admits he essentially aimed it at himself.
"But this ludicrous, unfeasible project had just one thing going for it, which is that you could read and enjoy it and get something out of it without having seen the film. I'm quite keen on that, generally, with books that are brought into existence by virtue of their relationship with something else but then they achieve some kind of independence from its original source. I also think the test of good non-fiction is the extent to which the book is able to engage you irrespective of whether or not you've got any interest in the subject."
Indeed, with the movie largely unavailable on DVD in most countries, let alone shown in cinemas, Zona stands to be more widely experienced than Stalker itself. "It's in a weird limbo in terms of its distribution," says Dyer. "You could wait for the Holy Grail of a nice print but that would be crazy. I gather that one of the ways you can see it in America now is online. But it's a much more immersive experience when it's actually projected on to a screen and it's a film you have to be immersed in, otherwise you could easily become frustrated by it."
With the 80th anniversary of Tarkovsky's birth this month, it seems like an ideal opportunity to reappraise the late film-maker's considerable oeuvre. "They're mad not to tie it in with that but it looks like it's not going to happen," says Dyer, who wasn't tempted to delay Zona until Stalker is re-released on DVD in Britain later this year.
"There was no way we were going to put back the publication of the book. I've done my bit for Tarkovsky, so now it's a question of what Tarkovsky can do for me."
Although he has been tempted to revisit it, Dyer dismisses the notion of releasing an updated edition at a later date. "I've never written a book before where so soon after it was published, I've wished I could go back and re-write passages of it, as I've either noticed new things about the film or been told stuff about it that I missed," he says.
"But that's symptomatic of the film's absolute inexhaustibleness. Generally when I write a book, I feel like I've worked stuff out to my satisfaction but with Stalker, the film has retained so much of its mystery."
Often branching off on esoteric tangents, Zona's frequent footnotes bring to mind a DVD commentary. "I can see it can be frustrating but in terms of what I was doing with the structure of the book, that was the only way of reconciling the ongoing summary with the other stuff," explains Dyer.
"What happens as the book goes on is that the distinction between the footnote-type stuff and the stuff in the main body of the text tends to collapse. By the end, when they're on the threshold of the Room and there's all this stuff about trying to achieve your deepest wish, that all ends up in the main text because by then the physical journey to the Room has come to a standstill. That enables me, in tandem with the film, to load that journey with more stuff than I could at the beginning."
Dyer says he is not a fan of traditional science fiction.
"Reading wise, I've never been able to read sci-fi because it seems so badly written, although I'm told there are some great sci-fi writers," he says.
"In terms of films, I actually like sci-fi but one of the problems for me when I first went to see Stalker was that I thought it was going to be more sci-fi than it was. If you go to see it wanting it to be sci-fi, you'll end up feeling let down by it."
Zona (Text Publishing $30) is out now. Geoff Dyer is a guest at the Auckland Writers & Readers Festival, Aotea Centre, May 9-13.
