The Magic Island is an account of Seabrook's experiences with Haitian Vodou in Haiti, and is considered the first popular English-language work to describe the concept of a zombie, defined by Seabrook as "a soulless human corpse, still dead, but taken from the grave and endowed by sorcery with a mechanical semblance of life—it is a dead body which is made to walk and act and move as if it were alive."

Drawn by whispered tales of voodoo, the characters immerse themselves in Haitian life, traveling through dark jungles and bustling towns. They experience mesmerizing ceremonies, which are summoning the unseen forces and resurrecting the walking dead. Seabrook captures these rites in vivid detail, revealing both the deep cultural significance and the uncanny aspects that hold readers spellbound. Throughout his daring investigation, he grapples with ancient beliefs and modern misconceptions, forging a narrative that blends anthropological study, travelogue, and eerie storytelling, leading to unsettling revelations and discoveries.