Haven by Emma Donoghue

In this beautiful story of adventure and survival from the New York Times bestselling author of Room , three men vow to leave the world behind them as they set out in a small boat for an island their leader has seen in a dream, with only faith to guide them.
In seventh-century Ireland, a scholar and priest called Artt has a dream telling him to leave the sinful world behind. Taking two monks—young Trian and old Cormac—he rows down the river Shannon in search of an isolated spot on which to found a monastery. Drifting out into the Atlantic, the three men find an impossibly steep, bare island inhabited by tens of thousands of birds, and claim it for God. In such a place, what will survival mean?