The book:

The Light Between Oceans by M L Stedman
Published by Black Swan in 2013
Pages: 434
My copy: Lent to me by my sister

The blurb:

A boat washes up on the shore of a remote lighthouse keeper’s island. It holds a dead man – and a crying baby. The only two islanders, Tom and his wife Izzy, are about to make a devastating decision.
They break the rules and follow their hearts. What happens next will break yours.