The last resort - Alison Lurie

Jenny has devoted her life to her husband, the naturalist Wilkie Walker. She is as rare a creature as the endangered species he works to preserve. But this year, as winter comes on, Wilkie seems distant and depressed. In desperation Jenny persuades him to visit Key West, but the sun and tropical scenery do nothing to cheer him up. As he grows even stranger, Jenny becomes involved with some exotic local characters - including Gerry, an ex-beatnik poet, and Lee, the dramatically attractive manager of a women-only guest house.