Maguire hadn't read the novel before Luhrmann approached him for the part of Nick Carraway, and takes the view that, "like with Shakespeare", everyone should relax and allow for multiple interpretations. "Do whatever you want. Make a cubist version; break it apart, deconstruct it. Whatever way you see it, it's art: you can do anything." He says this slowly, with the wry, slightly hoarse delivery that lends itself to creaky voiceovers and coming-of-age revelations: The Cider House Rules, Wonder Boys, The Ice Storm and now, saying some of the most famous lines ever written, Gatsby.
So what did he think? "I haven't read a lot of great novels and I look forward to reading the ones that I get myself to," he says. "So, er, I don't know. I get that it's held in very high regard and cited often as the greatest American novel, and people call Nick Carraway one of the greatest narrators and all that, and I appreciate that. But at the same time…" He bursts out laughing. Maguire clearly felt under no particular pressure to have a profound reaction. "I'm just a guy reading a book."
Carraway is the still eye of the picture, and to that end Maguire is perfectly cast. In interviews at least, he has been known to be still to the point of aggression: in publicity for Spider-Man, he stuck to an impressive range of one-word answers in response to almost any question asked of him. "I have some preciousness tendencies," he says, smiling. "But ultimately I want to be productive, so I try not to let that stand in my way."
This version of Gatsby will divide people. The aim, producers said, was to create a party "that kids wanted to come to", and so Jay-Z is an executive producer and the soundtrack is full of Beyoncé, Lana Del Rey and Jack White. Maguire is very good as Carraway, with that affable, principled, mildly diffident air he has come to specialise in. It's a tricky role to pull off since, as Maguire says, "Nick is an observer, so he is watching a lot of this happen. If you just filmed it, Nick wouldn't be doing much. And so my thing was: how do we dramatise Nick's experience? How do we make him active? And so that burst out the sanatorium idea."
In this particular version, Carraway is telling the story to a psychiatrist, in a rehab clinic long after the events, and reflecting on his friendship with Gatsby. Maguire's own friendship with DiCaprio lends a certain authenticity to their exchanges. The two men go back a long way, having met as teenagers at auditions in the 1990s, most of which DiCaprio won at Maguire's expense, although Maguire sometimes landed a smaller part (in This Boy's Life, for instance). Later, DiCaprio would recommend his friend for parts when he could. They must, over the years, have measured themselves against each other and now, Maguire says, "Our lives are very different." At 37, Maguire is married (to jewellery designer Jennifer Meyer, whose dad, Ronald, runs Universal Studios), with two children, Ruby and Otis. DiCaprio, 38, is still dating models.
We're both really competitive people," Maguire says. "I think we have a lot of confidence in our own individual paths, so whether it's with each other, or other friends of ours, we root for them. We're fans of our greatest competitors. We can joke with each other about competition, but are supportive. I have a whole bunch of friends like that. I'm glad that's the culture of my group."
This would sound gilded – and I'm sure there have been times when Maguire, coming up in DiCaprio's shadow, wondered if he would ever shake the guy off – but you believe him on the subject of solidarity. Carey Mulligan, who plays Daisy Buchanan in the film, first crossed Maguire's radar before she was famous; she had "self-taped an audition for the film Brothers", he says, which Jim Sheridan was making with Maguire in the lead. Natalie Portman was the heroine, and Mulligan had a small supporting role. This was before An Education came out and, "She was just thrilled to sit at the motel by the side of the freeway for six weeks to do her couple of days." When they parted, Maguire told her, "'I'll be looking out for you.' Which was just meant as encouragement, but she reminded me of it the other day. And when a friend of mine was making a film called The Greatest, I said, 'Carey is terrific and will be really reliable for you.' People did that for me coming up."
Maguire seems at home in The Great Gatsby, and in the role he inhabits. He knows what it is to be on the outside, perhaps. He had a peripatetic childhood. His parents were 18 and 19 years old when they had him, and he moved around various towns in California while growing up. Resources were scarce, and by the end of his teens he had a drink and drugs problem. He understands intuitively that the class system in the US is inflexible, despite protestations by politicians to the contrary. "The idea is that equal opportunity and social mobility in this country are as easy as pie. But [my sense is that] people jumping classes socially is at a low point. And it's not just what opportunities there are; it's what the attitudes are – it's about your ability to imagine a different future for yourself, and I think that's more difficult to do now."
It's partly a question of logistics, he says. He recalls from his own childhood that when you're spending all your energy just trying to get by, you have nothing left over with which to conceive of a future. "It's about having your brain space occupied by worrying about what I'm going to eat or how I'm going to pay rent, which is something I have contended with in life. Once you're not having to worry about that on a day-to-day basis, it allows you space to think about other things."
How poor were they? "As a kid, I was very poor. I mean, it's all relative, but we would get groceries from neighbours. I always had a roof over my head, but I slept on couches of relatives, and some night we wandered into a shelter. My family had food stamps and government medical insurance. And I wanted to get out of that, so my ambition was initially to make money; I was pretty driven."
Was he ashamed to be poor? "I wasn't around very wealthy people, but I did think I wanted to be able to be invited into their world."
Maguire is a pragmatic guy, which makes the fact he focused on becoming a movie star strange; the odds are less good than winning the lottery. If he wanted to make money, why not go to law school?
"It's so funny; I was in a meeting with a couple of people who'd experienced some unlikely success, like myself, and we were talking about how the odds weren't great. And that doesn't faze me at all. It's like Kennedy talking about us getting on the moon. Right? We actually didn't know how to do that yet, but he just goes, 'All right, before this decade is out, let's get there. We're going to do it.' That's sort of how I see things. Your imagination is not tethered to reality, or infrastructure, or statistics. What is any of that, anyway? I think our lives are a product of our imaginations."
And he knew he had talent. Maguire went to drama classes and, helped by the fact that he looked young for his age, started getting work in commercials and on TV shows. "I'm a realist in some sense. I'm not going to pursue being in the NBA or something – I know that's not going to happen. But if [there's something] I really want, I could find a strategy and put the work behind it to go and achieve that, whatever the odds."
He has been very strategic in his career. When Spider-Man came up, he had a few other choices on the table and tried to figure out which would deliver the biggest return and, as he said at the time, "open up more doors". Maguire had become stuck as the go-to guy for elegiac young men trying to find themselves in period dramas, and although he was very good in The Ice Storm, opposite Michael Caine in The Cider House Rules, and with Michael Douglas in Wonder Boys, it was starting to get old. Spider-Man was a wise decision: the other two films in contention at the time were Hart's War, a second world war action movie that ultimately starred Colin Farrell and Bruce Willis, and bombed, and the crime drama Training Day. That did OK, but nothing compared with Spider-Man, which went on to be the fifth biggest-grossing film of all time in the US and spawn a franchise.
"I'm self-aware enough to understand that it's statistically very hard to achieve the position I'm in," Maguire says. "But I also think I have a lot of ingredients that are right for the path that I've chosen. I find the way, like water; I like to be productive. I'm constantly reflecting on personal progress. And since I was around 15, I knew I'd be successful. Since I was 17 or 18, I always knew I wanted to live a great version of my life. And so I got those ideas, and they have been north stars to me."
What happened with the substance abuse? "I stopped consuming any mind-altering substances when I was 19 years old. And I've been abstinent since then."
Not even alcohol? "Not at all. And I'm a vegan. Maybe I eat a little too much sugar and wheat, but I'm trying constantly to refine."
His children live in California and, because of his own background, he tries to keep things stable for them, although, "I moved around so much and I've continued that in my career. I'm an actor – we go away for a few months and set up our world. And I want my kids to stay in school and make their friends and do all that. But I also appreciate travelling and having different experiences. And though I don't mind the idea of making some sacrifices, I also want to go pursue my career at the same time. I try not to make decisions based on conditioning."
He is an engaging combination of boyish wonder and conscientiousness, which has clearly stood him in good stead, along with his resistance to ageing. "I don't even know how old I look any more. I did look very young. I see kids driving and think, 'Oh God, they look 12.' I was one of those. But I seem to get consideration for characters my age these days." And he is spared the worst excesses of DiCaprio's fame; there are advantages to being the Nick Carraway figure, off to one side, shrewdly taking it all in, while those around you burn out. A guy reading a book, figuring out his next move.