I am reading (on my Kindle) The Lost City of Z, about the famous (or, used to be) explorer Percy Fawcett (he served as the role model for Professor Challenger in The Lost World by Conan Doyle).
Percy Fawcett was the last of the great Victoria age explorers. Many times he would head off into the
Amazon basin to explore some uncharted area, coming out again months later. Several times he was given up for lost only to reappear, weak and emaciated, but game to go back in again.
Fawcett developed a mania that within the huge expanse of the Amazon basin (the size of the United States) was a lost city that he called Z (which Doyle called The Lost World). The prevailing theory was that the Amazon basin could not support a large civilization (the Incas, Mayans, etc., were not in the Amazon basin) due to the poor soil and lack of food (that surprised me about the soil; however, I guess that soil fit for a jungle is not necessarily good for growing food). Fawcett became convinced that there had been such a civilization at one point, now covered by the jungle, and he aimed to find it.
Fawcett entered the Amazon one last time at age 57 in 1925, accompanied by his son and one other man (Fawcett believed in small groups). They were never heard from again, although people kept expecting him to emerge, victorious, for many years.
Over the decades other groups have entered the Amazon determined to find out what happened to Fawcett, only to not return themselves.
If you read the National Enquirer, etc., you may have recently seen photographs of Brad Pitt with a beard: he is making a movie based on the book. I assume he plays Fawcett.
Thus far an excellent read. The book shifts between a history of Fawcett, and the authors research and preparation to go into the Amazon basin himself. I have not finished the book, so I have no idea of he actually found Fawcett still wandering around, or if the author himself is now lost in the jungle or perished.