The Night Mark by Tiffany Reisz

A young woman ends her loveless marriage after both admit that she can't get over her first husband who was her soulmate. She feels cast adrift and takes a job photographing some local landmarks at the coast. She feels drawn to a painting and to the lighthouse and as a result goes to the island and gets swept out to sea landing back in time. It comes as no surprise that the lighthouse operator is her first husband's doppleganger and soon she is quite happy adjusting the rustic life on the island. Fate being what it is her time back in time is not as simple as it seems and she must make a determined choice to free herself and others from her past. This is not a simple time travel story but one where the lives of several people are intertwined. The historical portion of the book and the operation of the lighthouse is fascinating.