Correction: Print versions of this book review misstated the last name of the author in a photo caption. She is Ann Patchett, not Ann Pritchett.

Ten years ago Ann Patchett wrote herself onto the literary map when she took us to South America in “Bel Canto,” a novel that improbably mingled romance, terrorism and opera to win popular and critical praise. Like some exotic, undiscovered creature, the book resisted classification: not so much a literary thriller as a thrilling piece of literary fiction. Now, “State of Wonder” takes her to Brazil, into the Amazon’s piranha-infested waters, and the result is another dazzling work. As gripping as it is thoughtful, it burns with the low-level fever of “Heart of Darkness,” but its most febrile moments soar into the creepiness of “The Island of Doctor Moreau.”

Patchett’s genius here is her ability to lure ordinary people down the river of bizarre circumstances so gradually that they don’t look for an exit until the forest is thickly knotted behind them. The story starts in Minnesota at a large pharmaceutical company, a setting at once pastoral and clinical, bright and cold — in every way different from the tropical biome of anacondas, vampire bats and yet-to-be-identified plants and animals where most of this fantastic adventure eventually plays out.

A scientist named Marina Singh receives word that her office partner has died while visiting the company’s research lab somewhere in Brazil. The tragedy of that news is compounded by the curt letter that announces his death. On a blue aerogramme now two weeks old, the lab director has written: “Given our location, this rain, the petty bureaucracies of government (both this one and your own), and the time sensitive nature of our project, we chose to bury him here.” Eager — possibly too eager — to retrieve the body and discover what progress the lab is making toward development of a revolutionary fertility drug, the company chairman prevails upon Marina to fly to Brazil and investigate.

That journey “to the beating heart of nowhere” takes up more than half the novel, but it’s time Patchett uses to explore Marina’s past and her anxiety about confronting Dr. Swenson, the caustic director of the jungle laboratory. This is, among several other fascinating themes, a story about mentors and how they keep us in thrall long after we seem to have taken control of our lives. Marina hopes she doesn’t remember, but the older woman was her supervising physician years ago in Baltimore when their careers intersected one tragic night.

Although the director is no Mr. Kurtz, Swenson is “the uncontested kingpin” who greets Marina after an arduous journey into the jungle by saying flatly, “You shouldn’t have come.” Like John le Carre’s The Constant Gardener,” “State of Wonder” explores the unsavory behavior of Western pharmaceutical firms in Third World countries, but Patchett’s microscope is more finely calibrated to observe the strange choices individuals make in the remote wilderness of their own conscience.

The result is less an expose of a vast corporate conspiracy than a revelation of human nature. Removed from the inconvenience of financial, legal and ethical oversight, Swenson has spent years pursuing her own medical vision, and she confronts Marina with both the power of her authority and the logic of her private morality. Is the famous doctor exploiting primitive people for her employer or protecting them? And in any case, will the chaotic fecundity of nature prevail over any efforts to tame it in a petri dish?

Swenson grows more fascinating with each development in a story pregnant with surprises and reversals. She treats Marina with startling condescension, thwarting all her efforts to discover what really happened to her dead office mate or how their medical work is progressing. “No one tells the truth to people they don’t actually know, and if they do it is a horrible trait,” Swenson says bitterly. “Everyone wants something smaller, something neater than the truth.”

And yet when Marina pushes for the truth, she feels like Oliver holding up his bowl, pleading for more. All she gets are more pompous slap-downs: “I keep hoping that you are more than you show yourself to be,” Swenson says. “I am just on the verge of liking you but you dwell on the most mundane points.” Rude and intolerant but then surprisingly perceptive and compassionate, she’s as mysterious as anything in this alien place, and her caustic critique of modernity is so unsettling and persuasive you’ll find yourself falling under her spell, too.

Nothing is as it seems in this surreal jungle hideaway at the center of a story that shifts unpredictably from the tragedy of Orpheus to the mordant comedy of “A Handful of Dust.” The psychedelic plants might offer death or immortality; the natives are as likely to welcome strangers as they are to shoot them with poison darts. Patchett’s creation of this foreign culture and its symbiosis with the fauna of a lost world is one of the novel’s most captivating elements. And the hallucinatory side effects of malaria medication ensure that sleep offers Marina no escape from strange visions.

Loaded as the story is with profound ethical issues, Patchett also knows when to pack light to keep the adventure moving. In fact, as the end approaches, “State of Wonder” crashes toward a breathless conclusion as though she’s being chased by a swarm of Amazonian wasps. This is surely the smartest, most exciting novel of the summer.

Charles is The Post’s fiction editor. You can follow him on Twitter @RonCharles.

Ann Patchett will be at Politics and Prose Wednesday at 7 p.m.

state of wonder

By Ann Patchett

Harper. 353 pp. $26.99