While a children's book, a good read for someone in grades 2 through 4, I learned of it only recently, and have an interest in the Ra voyages. Overall, it is a worthwhile introduction to Thor Heyerdahl and his Atlantic expeditions.
From the standpoint of a child, this is a good book, a relatively quick read, at 64 pages, many of them with black and white photos from the voyage. The story gives an overview of planning by Thor Heyerdahl for the first trip and the two voyages, touching on some of the hazards and challenges faced by the sailors.
The tone of the book is upbeat, noting Thor's view that it was necessary to have sailors from different nations and cultures to show how they could get along even under harsh and trying circumstances. To that end, he sailed under a UN flag to show global harmony and unity, something that seems very distant in the halls of that organization these days.
For someone who likes adventures, these trips are certainly great ones, of the relatively modern era, with Thor having sailed in the late 1960's and 1970's.