It's called The Viking and The Red Man, it's written by Reider T. Sherwin and after I read it I googled it and found out that a lot of other people like it too. Although not for the same reasons as me―To put it mildly. And I was overwhelmed by the feeling that somebody should set the record straight.
Great mystery man solves great mystery
Reider Thorbjorn Sherwin was born in 1894, and wrote his series of books in the 1940s and 50s. There is not a lot of biographical information available, except that he claims to be born in Norway (probably as Reidar Thorbjørn Skjerven), and he seems to have lived all his adult life in the United States, possibly New England. I can find no trace of where in Norway he might have been born, when he arrived or what he was doing up until 1940 when he published his first book. In it he claimed to have solved a mystery that had already puzzled learned men for centuries: The 15th century disappearance of the Norse Greenlanders.