This is a competent review and reconstruction of the history of European exploration of the lands bordering or within the North Atlantic. The structure is odd, the author beginning backwards with the Portuguese and Spanish, through the Bristol fisherman and the Norse, to end with the Irish Celts to whom he credits first landfall on Iceland, Greenland and N. America. Then, after his expository chapters, he ends with a recap of the whole history, in order this time, in his concluding chapter.
Some of the author's conclusions are debatable. That the Norse briefly settled North America is universally held, but that 'Vinland' was in New England--southern New England at that--is contestable. That the Irish had already settled Iceland before the Norse is generally accepted, but that they made it westward to both Greenland and North America is dubitable. This notwithstanding, Sauer appears atop the sources, his judgments meritorious.