The October book is The Light Between Oceans by M. L. Steadman.
From Publishers Weekly:
In Stedman’s deftly crafted debut, Tom Sherbourne, seeking constancy after the horrors of WWI, takes a lighthouse keeper’s post on an Australian island, and calls for Isabel, a young woman he met on his travels, to join him there as his wife. In peaceful isolation, their love grows. But four years on the island and several miscarriages bring Isabel’s seemingly boundless spirit to the brink, and leave Tom feeling helpless until a boat washes ashore with a dead man and a living child. Isabel convinces herself—and Tom—that the baby is a gift from God. After two years of maternal bliss for Isabel and alternating waves of joy and guilt for Tom, the family, back on the mainland, is confronted with the mother of their child, very much alive. Stedman grounds what could be a far-fetched premise, setting the stage beautifully to allow for a heart-wrenching moral dilemma to play out, making evident that “Right and wrong can be like bloody snakes: so tangled up that you can’t tell which is which until you’ve shot ’em both, and then it’s too late.” Most impressive is the subtle yet profound maturation of Isabel and Tom as characters. Agent: Susan Armstrong, Conville & Walsh. (Aug.)