With Navola (Knopf, July), Bacigalupi turns from climate fiction to epic fantasy.

What were the origins of this book?

It started as a bit of creative play. It wasn’t intended for publication. I would play around a little bit, then walk away and come back—and over time it started to grow. You see the different pieces of that in the book—now we’re going to have a myth, or there might be a song. At some point I ended up with just a vast amount of written words. It had become so big that it actually did look like a book-thing. So then I worked on it again with a much more intentional eye toward making it into an actual book-like object.

How did you approach the Renaissance Italy–inspired worldbuilding?

The seed was probably a book called Medici Money about the early stages of merchant banking and the basic mechanisms of capital that are taken for granted in our society but were new innovations at the time. There’s also this classic fantasy trope of digging into the past and unearthing old knowledge, which is the weird, interesting thing about the Renaissance: they were digging up these old Roman and Greek texts, figuring out architecture, mathematics, and political philosophy. The other component of it was that, at an early stage, a friend of mine was going to Italy to study Italian. And he out of the blue said, “Do you wanna come with me?”

How did you integrate the magic?

I like magic that feels numinous, mysterious, and hard to categorize. I think of it as thread inside a tapestry. A little bit of gold thread running through catches your eye and holds you, but you don’t want the whole thing to be gold. Magic should feel magical: genuinely something that you wish you understood more about but probably never will.

You’ve called writing this an escape. How so?

Almost all of my career and reputation was built on climate fiction. If you’re going through regular life, and you’re anxious about the state of the world or the future, and then you sit down and spend all your creative time building those worlds out to their worst degree, you spend all your time in unhealthy places. In Navola, there’s a moment where I write about glaciers that are unchanging. They’re un-melting. There’s something that feels almost sinful about working outside of a climate-changed world. The ice remains. That’s extraordinary.

The plot is still quite dark though.

All my characters can be plotting and poisoning each other, and that still is fairly relaxing in comparison to thinking about the end of the world. I think maybe what calibrates for me as relaxing might be different than what calibrates for other people? I have a lot of spiders in my head or something.