Gregor and the Marks of Secret

by Jonathan Stroud

Like Gregor, this book builds an intricate hidden world with its own politics and power structures—but Stroud layers in a magic system where knowledge itself becomes currency. You'll recognize that same tension between young protagonists learning to navigate adult conflicts, except here the stakes involve summoning djinn and navigating London's magical underworld.

by Gary Paulsen

I'm recommending this 1987 survival story because it shares Gregor's unflinching approach to danger—there's no sugar-coating here, just a young person forced to problem-solve under genuine threat. Where Collins gives you an underground civilization to decode, Paulsen gives you raw wilderness, but both demand that their protagonists think strategically and adapt quickly to stay alive.

by George MacDonald

This is a quieter fantasy than the Underland Chronicles, but it shares something crucial: a protagonist learning to navigate a complex society with competing factions and hidden rules. Where Gregor fights battles, Maia fights court politics with the same intelligence and determination—and Addison's intricate worldbuilding rivals Collins' in its attention to how societies actually function.

by Richard Adams

Published in 1972, this epic follows a band of rabbits on a dangerous journey—and like the Underland Chronicles, it takes its non-human characters with absolute seriousness, giving them agency, strategy, and genuine moral complexity. Adams doesn't anthropomorphize cutely; he builds an entire civilization with its own history and conflicts, much like how Collins treats the Underlanders and Nibblers as fully realized societies.

by J.K. Rowling

I know this seems obvious, but hear me out: this is where the Harry Potter series shifts into something closer to what you loved in Gregor—darker, with genuine political stakes beneath the adventure. The tournament structure mirrors how Collins uses Gregor's missions as a framework for exploring larger conflicts between factions, and Rowling's willingness to let characters die and consequences matter aligns with Collins' unflinching tone.