Ballantyne eventually wrote more than a hundred books, most of them adventure stories for boys, distinguished by accurate, firsthand detail. He was famous for thorough research: he climbed lighthouse towers, descended into coal mines, and trained with firefighters before writing about them.
His most celebrated work, The Coral Island (1858), follows three shipwrecked boys on a tropical Pacific island. It became an enduring classic, influencing Robert Louis Stevenson's Treasure Island and later serving as the ironic target of William Golding's Lord of the Flies. Among his many other popular titles are Ungava (1857), The Gorilla Hunters (1861), The Lifeboat (1864), The Lighthouse (1865), and Fighting the Flames (1867). His straightforward prose, moral earnestness, and thrilling plots made him one of the most popular children's writers of the Victorian era.
Ballantyne died in Rome in 1894, remembered as a founding figure of British adventure literature.