Greg Egan does not make this easy on you, and I went in knowing that from a couple people who’d warned me. The setup: an experiment testing a theory of quantum gravity goes wrong in the most literal way possible, replacing a region of ordinary space with a new vacuum state that expands outward at half lightspeed, eating stars as it goes. Centuries later, people live near the border studying it, and the plot follows a disagreement about whether to try stopping its expansion or understanding it first.

The physics is the star of the show here, more than any character, and Egan clearly wants it that way. Schild’s ladder itself, the mathematical technique the title borrows, gets worked into the structure of the book in a way I found genuinely elegant once I understood what it was doing, even though understanding it took real effort on my part and I don’t read much hard SF as a rule. Where the book struggled for me was on the human side of things. The characters in this future have moved past bodies into something more abstract, and while I understand that’s the point, a species examining questions of identity and continuity once the old anchors of embodiment are gone, it left me with almost nothing to hold onto emotionally. There’s a central relationship that’s clearly meant to carry weight, and its most important moment gets resolved with what felt like a shrug, no real payoff for the tension that had been building.

I don’t regret reading it. The ideas about identity politics stretched to their logical extreme, worked out decades before that phrase meant what it means now, are the kind of thing that would blow some minds if more people actually finished the book instead of bouncing off the density in the first fifty pages, which I nearly did myself. But three stars feels right. This is escapism for readers who are already fluent in the physics, and I was working to keep up more than I was enjoying the ride.