Hy Brasil - Margaret Elphinstone

After fraudulently winning a writing competition, Sidony Redruth is sent by her editor to write the first-ever travel book on Hy Brasil, a near-mythical island somewhere in the Atlantic, whose very existence has been a matter of debate as late as the nineteenth century.
Elphinstone's plot takes the island location as its starting point, throws in some old-fashioned piracy, a lost treasure, modern-day drug smuggling, political intrigue, an active volcano and a tragic love affair. Told through Sidony's notes for her book, Hy Brasil has all the elements of an adult adventure story, but it is also a contemporary thriller with literary influences ranging from The Tempest and Treasure Island to Moby-Dick.