Explorer Sir Quidby Forsythe III has made a habit of disappearing. Though he’s been presumed dead before, this time it may actually be true. He’s left behind his 15-year-old grandchildren, Ozzie and Alex, who live in a decommissioned lighthouse off the coast of England. While Sir Quidby’s “pursuit of debunking” has sparked his share of enemies, the twins are still surprised when assassins raid their grandfather’s funeral. Ozzie and Alex find safety aboard the airship Angeluswith probable allies who are convinced Sir Quidby is only missing and needs rescuing. He’s likely in the place he regularly explored—the Terravenum, once part of an immense world with Earth until wars split them apart. The Terravenum brims with a wide range of creatures, including evil mutant kittens and Layla, an upright, goggles-donning lizard. She helps the twins evade Skhaar the Annihilator, who has a tendency to disembowel subordinates who fail him. What Skhaar—and many others—want is Sir Quidby’s enigmatic journal, which Ozzie and Alex must fight to keep out of villainous hands. Abbott jampacks his delightful series opener with varying species, extraordinary weapons, and curious places, like Aeronoth, a sky city. It’s a lot to take in, especially as the story hits the ground running with the twins stumbling from one frenzied action scene to the next. But the author pulls the reins just enough to further develop the charming protagonists—athletic Alex and nerdy Ozzie. Though violence seems second nature in the Terravenum, the book is mostly a comedy, from misspoken passwords nearly triggering a “death duel” at a library to goofy, often irrelevant footnotes. The sequel may deliver much more information regarding the twins’ parents’ supposed kidnapping years ago and a powerful baddie whom characters name-drop. The story ends on a stellar cliffhanger.