The book is a thrilling account of a daring and adventurous expedition across the Pacific Ocean on a balsa wood raft named Kon-Tiki. The journey, led by a Norwegian explorer, is an attempt to prove that South Americans could have settled Polynesia in pre-Columbian times. The narrative is filled with descriptions of dangerous encounters with marine life, harsh weather conditions, and the challenges of surviving on the open sea. The expedition's success provides compelling evidence in support of the author's theory.