From "The weirdest book in the world just turned 40. We talked to its creator", by Chris Kaye, interviewing Luigi Serafini, Insider, 2021-11-23:
"I've been drawing since my childhood. My parents were worried because I was drawing all the time. Like a disease, drawing for me. I preferred making drawings rather than playing with friends," he says. "So drawing for me was better than talk. When I draw, I enter into another dimension."
[...]
"So I don't know why but at a certain moment in my life, I started making pages of the Codex," Serafini continues. "And I always tell this story: an old friend, he invited me to a movie. I answered to him, 'I can't because I'm making an encyclopedia.' But I didn't know why and what I was drawing."
[...]
"40 years after, I keep drawing the pages of the Codex. It's a need for me, but I do other things also. I don't make only pages of the Codex. But I could make a page every day," he says.