"He operates by the rules and she operates by her own code of what's right and wrong. I don't think that makes her vengeful, it makes her a realist in her own world, it makes her consistent."
"He becomes less civilised and she becomes more so. There's a point in the story, where she asks permission - 'May I kill him?' That’s a huge change for her, and a huge change for him to say, 'Yes.'"
If the ghost of fabled author Stieg Larsson is weighing heavily on the shoulders of the man charged with bringing his words to the big screen, he's not showing it. Zaillian's only concern right now is getting a decent, very strong coffee...
"Sorry, I have to have this," he apologises in London. "The thing is, I'm not thinking about any of that, when I'm sitting in the room by myself - I'm just thinking about getting to the next scene.
"When I work on anything, whether it's this or a book that no one has read, something like Awakenings, I do the same thing. What I'm trying to figure out is if I understand it enough to be the person to do it."
Another thing he doesn't think about is the benefit of bringing another version of Dragon Tattoo to the screen when, as well as the books in circulation on every holiday villa shelf in the land, there is a very popular big-screen trilogy in native Swedish, still fresh in fans' minds.
"From the studio's point of view, it's a no-brainer," he replies equably. "The Swedish version was successful in the US, it made $10m. If THIS film does that, there's not going to be part two.
"But, aesthetically, for me it was very important not to make a remake. I didn't see the film, and I still haven't. I'm free of that, I'm adapting the book again as if it's the first time, and then we'll see if other people..."
Dragon Tattoo comes hot on the heels of Zaillian's script for Moneyball, Brad Pitt's well-received baseball drama. This seemingly prodigious output is an illusion, apparently.
"It may feel like one a week, but I promise you that's far from the truth. It's written into my contract that people can't bug me for a first draft until at least six months has passed, and often it's a lot longer.
"I don't really enjoy the daily process of a lot of it, because I'm worried that I'm not going to be able to do it well, but when I'm done with it, I'm very happy. I obviously like the life of a writer, and it suits me."
And Zaillian obviously suits it, with an Oscar for his efforts on Schindler's List and a heaving in-tray of big-budget requests. Any pressure following such success?
"I don't have an Oscar staring at me, because it's not anywhere I can see it. I still have an office that has less in it than this hotel room. It's meant to be uncomfortable. I have a desk, I have a couch that I never use, and I have a coffee maker and that's it."
And, talking of which, he takes another dark sip.
Girl with the Dragon Tattoo is in cinemas now. Watch the trailer below: