I suppose as a pure adventure story it is compelling but that puts it at about the level of Felix Baumgartner jumping out of a space ship in terms of historical value. The peopling of the Pacific islands was a very settled question when Heyerdahl had his expeditions, and those expeditions provided not a whit of actual evidence to support his theory.

He was also more than a little racist towards Polynesians, the impetus of his theory was not far off "these savages couldn't have possible build these monuments".