The first book in this series, “Charlie Thorne and the Last Equation” pitted young genius Charlie against none other than Albert Einstein. In its sequel, “Charlie Thorne and the Lost City,” author Stuart Gibbs pits Charlie against Charles Darwin, and it’s not surprising that Charlie comes out as the more compassionate genius.

As with the first book in this series, there is not a dull moment to be had from the first page to the last. Gibbs again begins the story in the past, as we “witness” Darwin bringing a secret chest aboard the HMS Beagle. It’s a chest that holds something mysterious, something extremely appalling, that shocks his friend and captain of the ship. It’s also something that has remained secret until present time.

In the first book, Charlie solved Einstein’s clues and found his secret formula—a formula that could create powerful weapons—a formula that Charlie is determined to keep secret. She doesn’t trust the US government or the foreign governments who are seeking this out for their own gain. But when she is discovered in the Galápagos Islands, where she had been living a low-key life, she must flee. And just when the deadly Russian agent seems about to capture Charlie, her brother and his partner, both CIA agents, show up to save the day.

Charlie had just been shown a code carved onto the shell of a tortoise by Darwin that he promised would lead to the greatest treasure ever known by mankind. Her brother, Dante, and his partner agree to accompany Charlie to see what the treasure might be. Following the trio are several dastardly groups all out to discover the treasure for themselves. There is the Italian family whose ancestor sailed on the Beagle with Darwin, and whose family has been researching the treasure for generations. There is the Russian agent who would like to retire and live a life of comfort, and there is the amoral guy running an oil refinery in the Amazon, who would do almost anything to get rich.

Young Charlie manages to stay a step ahead of all the adults around her, although at the end, there is a twist that will catch most readers by surprise. This is a novel that is not just entertaining, but also educational — and touching. Charlie might be able to outsmart grownups, but she is also a caring protagonist and truly doesn’t wish to harm others, no matter their intentions toward her. Readers learn a lot of interesting facts about the Amazon and the Galápagos Islands, about evolution, and about Darwin.

This is exactly the kind of book that teachers love to recommend because kids will definitely enjoy it. And getting kids excited about reading is sometimes just a matter of finding them an author they love. I can attest that my students adore Stuart Gibbs’ books. They voraciously read the Spy School series and enjoy the humor and the action. It’s also worth noting that Charlie is a person of color, and Gibbs describes her by saying, “Charlie could pass herself off as a native of almost any place on earth, because ethnically, she was a mix of different races—although she didn’t look like one more than any other.” The text also notes that when she told people, on the same day, that she was “Thai, Greek, Kenyan, Guatemalan, and aboriginal Australian” no one questioned her. A child genius with dark skin who speaks over a dozen languages. What a role model for young readers.

Please note: This review is based on the final, hardcover book provided by the publisher, Simon & Schuster, for review purposes.