Recently a colleague asked if I could get an extra advance copy of the newest book in Rick Riordan's Heroes of Olympus series. It appears his young son had powered through Riordan's first Greek-gods-in-the-modern-world series, Percy Jackson and the Olympians, and the first two books of the second. He's dying to read The Mark of Athena, and he doesn't want to wait until October to get it.

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Unfortunately, I wasn't able to help them out with this, as Riordan and his publisher are not in the habit of making advances available. My colleague was dismayed. He begged me for suggestions of other books to assuage his son's certain disappointment.

What fun.

Thinking about "readalikes" for Percy Jackson sent me back to some of my favorites from growing up and also some more recent ones, notably The Underland Chronicles, by Suzanne Collins. This terrific quintet seems to have been forgotten in the frenzy surrounding The Hunger Games. It seems right, surrounded as I am by Hunger Games movie tie-ins, to spend some time remembering Gregor the Overlander. He totally rocks, and it seems unfair that he's being overshadowed by big sister Katniss.

Stuck babysitting his ailing grandmother and his toddler sister for the summer, 11-year-old Gregor is pretty put out. But he's dutiful, so he does the chores, including taking the laundry to his apartment building's cellar. While his back is turned, baby sister Boots accidentally loses a toy in a vent. He turns around just in time to see her disappearing through the vent, and, like a good big brother, he immediately follows.

The two children find themselves falling gently through an enormous space, eventually alighting in the Underland. This vast, underground world is populated by very pale people who ride giant bats and are at war with giant rats. And it turns out Gregor is a prophesied warrior, destined to lead a quest that will save the Underland. Maybe.

Collins gives Gregor a spectacular supporting cast that eventually includes, over the five volumes, giant cockroaches, giant ants, giant moles, giant mice, giant lizards and giant spiders—in addition to the aforementioned giant bats and giant rats. The bat Ares, who becomes Gregor's "bonded" mount is a complex and conflicted creature. Tick and Temp the cockroaches, Boots' devoted friends, prove to be noble companions. And Ripred the savagely charismatic rat rivals Templeton in his snarling misanthropy even as he wins both readers' and Gregor's hearts.

With prophecies flung at Gregor every time he descends to the Underland, Collins gives him adventure after adventure, exploring huge swaths of subterranean territory. These adventures are far from mindless fluff, as she gives readers plenty to think about. Do the ends justify the means? Does might make right? Is there such a thing as a just war?

As we wrote, in our review of the last book in the series, Gregor and the Code of Claw, "Perhaps Collins’s greatest achievement in these tales is the effortless introduction of weighty geopolitical ethics into rip-roaring adventure. It seems as elusive in the Underland as up above, but Gregor and his companions…may yet find a way. The resolution is bittersweet but faintly hopeful—a fitting end for an unflinchingly gutsy series whose deftly drawn characters have always lived dangerously."

Heavy stuff for a fantasy-adventure series aimed squarely at 9- to 13-year-olds, and Collins pulls it off effortlessly through that alchemy of characterization, plotting, pacing, worldbuilding and voice that makes for stellar storytelling. Will all those eager readers understand this subtext as they're gobbling up Gregor's quests? Maybe not. But they will probably find themselves remembering Gregor for years to come.

I know I do.

Vicky Smith is the Children's and Teen Editor at Kirkus.