This book was written by an anthropologist/ethnologist who spent some years talking to people of southwestern New Guinea, particularly Marind-anim, in the 1930s. He therefore published selected stories that he thought were particularly relevant to anthropological documentation (he said that he was interested in the "geistiges Leben" of the people), including mythology, supernatural stories, legendary history, and some accounts of recent events. It's only for the last of these that he names the people he got the stories from. He was particularly interested in documenting head-hunting, which colonial administration was in the process of suppressing at that time; there are a number of stories from participants in head-hunting expeditions, including two different accounts of one 1927 expedition. All of this is surrounded by lots of contextual notes, information, and commentary. Unfortunately, the commentary is about as condescending as you might fear. Still, it's good that someone wrote these things down at all.