The Scottish author moved to Lake View to be with his wife, a Chicagoan.

Irvine Welsh appreciates his crammed schedule: “It keeps me out of trouble. The devil finds work for idle hands and all that.” The mischievous Scot who was catapulted to fame by his 1993 novel, Trainspotting (the sequel was 2002’s Porno), just released the prequel, Skagboys (Norton, $27). He’s also consulting on a play, Trainspotting USA; a movie, Filth, based on his 1998 novel and starring James McAvoy; and several TV scripts (one Miami-set project involves Iggy Pop). Chicago talked to Welsh about his charmed literary life.

It’s been almost 20 years since Trainspotting introduced us to a group of young Scots whose lives are hijacked by heroin. Why did you decide to revisit the gang?
When I wrote Trainspotting, I hadn’t written a book before. I cut this chunk at the middle that I thought was just backstory—a novice writer’s way of writing. Years later, when I was moving, I found all these disks. The computer I wrote Trainspotting on had been lost, so I sent [the disks] away to somebody who could recover the material. It was like finding this treasure chest. The characters were innocent and hopeful; I wanted to chart their journey from being poppy young guys about town to leading this desolate life.

So you didn’t initially intend a trilogy?
No. Porno came about by accident. While I was writing it, I realized that the main character—I’d originally given him a different name—was actually Sick Boy. If you write characters who are strong enough and interesting enough, they’ll gate-crash into your future books.

You’re further removed now from the lifestyle of your characters. Was it harder to get in their heads?
When I started Trainspotting, I was 28, and it seemed that the distance between 24 and 28 was a million light years. I started Skagboys when I was 50. The distance between 50 and 22 doesn’t even seem like light years.

Skagboys debuted in the U.K. in April at the top of the bestseller list. Is there a difference in how British and American audiences react to your work?
I’m the British bad boy, and I’ve become a kind of airport novelist there. Over here, I’m still quite culty. Trainspotting was an arthouse film rather than at every multiplex like in Europe.

The play Trainspotting USA premieres in Chicago this month. How did you Americanize something so quintessentially European? [Director Tom Mullen readapted a 1996 stage version of the novel and set it in Kansas City; the script has new material from Welsh.]
Most American cities with drug problems, it’s all crystal meth now. But Kansas City has a more significant heroin problem, apparently.

Where do you write?
I work on the el quite a lot. I go all the way from Howard down to Dan Ryan and back up again. If you’re stuck on a character, you just see someone that comes on, and you’ve got a perfect description.

You’re setting a new novel in Miami. Any plans to feature Chicago one day?
Anybody can come into Miami and write about it. With Chicago, there are so many good writers who really understand the place. There’s culture that goes back so many generations—to come in as an outsider, you don’t always get the same flavor that people who are indigenous to Chicago would.

SEE THE PLAY: Trainspotting USA runs Oct. 16 to Dec. 2 at Theater Wit. 1229 W. Belmont Ave., trainspottingusa.com

Photograph: Jeff Sciortino