Lost in Shangri-La - Mitchell Zukoff

Perhaps the most remarkable part of this adventure story set in the later days of the Second World War is the consequences for the natives of the secluded area called Shangri-La that three American soldiers crash into - living a lifestyle unchanged for thousands of years, the natives are yanked into the 20th century. In the epilogue the author finds a few still clinging to their traditional ways (penis gourds, bones through noses) to sell their souls by posing for photographs with tourists.

In May 1945 twenty American military personnel (including women) go on a pleasure flight over a secluded section of Papa New Guinea but bad weather forces the plane to crash. Only thee survive and they are helped by the natives, who believe the Americans with their white skin are spirits. A group of Filipino-American soldiers parachute in to set up a camp and help the survivors, and eventually a daring rescue plan is crafted involving gliders, a near-forgotten aircraft nicknamed "coffin boxes".  A good summer time adventure read.