I half imagine that when I meet him, Shaun Tan will be a diminutive Australian Willy Wonka, all hat and cane and colourful outfits, with a strange and wondrous creature by his side. It isn’t disappointing exactly to find he’s a perfectly ordinary, softly spoken middle-aged man in a puffer jacket and faded black denim jeans; it just needs the slightest adjustment in perspective.

Tan is one of the country’s most cherished and awarded picture book illustrators, a master of surrealist suburban fantasy. His 2006 wordless graphic novel The Arrival won the New South Wales premier’s literary award, and he won an Oscar for the film adaptation of his picture book The Lost Thing. His books are filled with curious hybrid creatures and freakish, fantastical landscapes, but in person he’s positively sensible.

“In my day-to-day life, I’m not creative at all,” Tan says as we prepare to take his strange and wondrous creature – AKA French bulldog Reuben – for a walk in the local Brunswick West dog park near where Tan lives with his artist wife Inari. “But when I sit down to draw, it’s like a moment to pause and question: what does all this mean? And how come I live like this and not another way?”

These are the key existential questions that haunt Tan’s picture books, which often deal with themes of alienation, diaspora and the fine line between utopia and dystopia. Just how much of his work is intended for children is difficult to judge; dark in tone, with muted palettes and stormy horizons, Tan’s best work is nebulous and hard to categorise. It speaks to the child inside the adult; or perhaps that should be the adult inside the child?

“I have this theory that if a painting is really good a five-year-old can still get something out of it,” Tan says. “A good painting should hit you in an emotional way.” Often he will haul one of his kids into the studio to see their reaction to a piece he’s working on. “A bit happy and a bit creepy? Great, that’s what I wanted. You can go now.”

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We head around the corner of Victoria Street and towards the park, Reuben trotting along contentedly ahead of us. The afternoon is mild but the sky is a matt grey wash above us, blanketing the surrounding houses in a flat, utilitarian light. It has the grubby charm of the suburbia of Tan’s books, simultaneously familiar and uncanny.

Brunswick is “just kind of where we ended up”, Tan says as we reach the park and open the gate for Reuben to enter. “I’m an introverted person, so I’m not diving into it all the time, but my encounters with the community have been really positive.” Tan likes to draw little scenes and landscapes as a way of getting to know his environment, and in this way Brunswick is beginning to feel more like home. “I’m still tuning into it, I’m painting it and learning things about it.”

Born in Perth to a Chinese Malaysian father and Australian mother, Tan took to illustration early without quite understanding how central to his existence it would become. “When I look at my work from that time, it’s not that good. It’s not like I was supremely talented.”

What he had was enthusiasm, an interest that would become keener with time, and parents who were warmly encouraging. “They just said: you seem to love doing this.” They found a specialist art high school in the suburb of Balcatta for him, where he developed his unique craft. “I learned most of my basic artistic skills that I use today in high school. I don’t think I’ve had any formal illustration training since then.”

Tan was successful early, winning the L Ron Hubbard Illustrators of the Future award straight out of high school, and eventually the Hugo award, science fiction’s greatest honour. He doesn’t subscribe to the concept of born talent, preferring a mantra of grit and repetition. “I had an interest. And I think interest is talent because it keeps you doing the thing, and a thousand hours later, you’re actually better at it.”

Still, there is a kind of singularity guiding Tan’s work, as if every strand of an idea from every book he’s created is interwoven and hyperconnected. Even if he sees it more modestly: “I think you shouldn’t take it too seriously; it’s not a sacred universe where everything is just so. I use whatever I have to hand.” If creatures pop up in several books, or forms seem familiar, “that’s the limit of my ability, that’s what that is”.

Hometown is Tan’s newest work, the story of a teenage girl who feels pretty normal in her normal town until a stranger from a distant world arrives to tell her she doesn’t belong. From the opening panels introducing the girl’s family and friends – augmented by a terrifically sardonic tone in the text – its allegory is both achingly clear and brilliantly inconclusive.

“It’s got to be a bit unfinished and unresolved, and sometimes a bit unsettling. Sometimes I’ll finish a picture and it’s so resolved it’s no good. Everything is landing, [but] it leaves no residual echo in your mind because it’s so wrapped up. Most of the books and movies and cartoons I’ve enjoyed are the ones I don’t actually understand. That’s what keeps me thinking about it.”

The grey has settled over the park but the place is suddenly buzzing. Tan bends down to let Reuben off his lead and by the time he’s upright again, Reuben has bolted, tearing around a group of bewildered dogs several times his size in quickening concentric circles, like a creature from one of Tan’s books. “Reuben is an electron: he orbits the nucleus of action,” Tan laughs.

The conversation orbits too, back to the question of reality and the thin veil between worlds that exists for all of us. “I have the same problem as everybody else: it’s hard to penetrate the veneer of familiarity. We’re always only seeing a thin skin of reality, which is what an illustration is, just another thin skin. And that’s the world around us, it’s only paper thin.”

Tan’s enduring interest in the mechanics of life (at one point he envisioned becoming a geneticist) has led him to think of reality as “arbitrary. I was very interested, as a young person, in science and quantum physics. It satisfied my suspicion that this is one reality amongst many.”

We look around the park to the horizon – horizons are important in Tan’s work, often for their absence – as if searching for signs of other worlds. “Look at those trees, they’re like lungs coming out of the ground. And there’s all this stuff going underground. Then all these paths are like organs in the body. The world is a collective organism. It works. I don’t know how, but it does.” For a moment, I feel I can see with Tan’s eyes, and the world does seem magical and weird.

We start to head back, Reuben under control and ready for home. As we pass local houses and apartment blocks, I get another glimpse of the world as Tan sees it, that way he has of peering behind the veil. “I like looking at the backs of buildings. Nobody aesthetically planned that; it just grew. Some people think that’s ugly, but it’s got a kind of beauty to it. It’s got its own composition.”

We reach the intersection and press the button. He looks like an ordinary person walking his French bulldog, his vast and idiosyncratic genius completely invisible to the outside world. I’m reminded of something he’d said earlier: “My workspaces, when I’ve looked back at it, have been very un-aesthetic, like dungeons. It doesn’t bother me because I’m not in the real world when I’m painting; I’m in another world. So the window is already in front of me.”