"Pure color!" wrote Paul Gauguin to his wife, Mette, from the South Seas. "Everything must be sacrificed to it." In Off Island, novelist Lara Tupper imagines Gauguin-chasing new light, new color-ran away to a new island, a rugged outpost off the coast of Maine.There, Gauguin leaves behind some paintings and letters, and maybe a child. And a hundred years later, another Maine painter, Pete, finds himself torn between his muses-the sturdy, reliable...