Sappho: A New Translation by Mary Barnard. The fragments of Sappho's poetry — only about 650 lines survive — are the most direct connection to ancient Mytilene. Barnard's translations are clean and modern without sacrificing the compressed intensity of the originals. Reading them on the island where Sappho lived and taught in the 6th century BC gives the fragments a different quality than they have on a library shelf.
The Birdwatcher by William Shaw. A thriller set partly on Lesbos during the spring migration, which uses the island's geography and the birdwatching community accurately and well. Not great literature, but a genuinely engaging read that captures the strange intensity of the spring passage and the landscapes of eastern Lesbos.
Lesbos: A Cultural History by Antonis Karatzas. A thorough historical survey from antiquity through the Ottoman period to modern times. The chapters on the Genoese Gattilusio family — who held the island as a Byzantine fief for a century before the Ottoman conquest — illuminate the Castle and the old urban fabric in ways a guidebook cannot.
Mytilene: The Town and its People by Strati Myrivili (translated). Myrivili was born in Mytilene in 1890 and his fiction, though set mostly during the wars, gives the most vivid account of the city's pre-war world — the Anatolian Greek community, the cosmopolitan harbour, the ouzo-and-politics culture that shaped the place for centuries.
A Carafe of Ouzo by Dimitris Tziovaras. A collection of essays and short stories centred on Lesbos, ouzo, and the particular quality of Aegean light. Untranslated but worth tracking down if you read Greek. For non-Greek readers, it at least serves as a reminder that Lesbos has a serious modern literary tradition.