I am writing a non fiction story of my adventure on hiking. I am doing my best to get most of the people to approve letting me write about them, but how much work should I put into having everyone's approval? Plus one main character, hasn't responded, and she's the one I'd imagine getting upset before anyone else.
If you are using their real names and/or making the character so that it is readily-identifiable as that person to people who know her, I recommend getting permission.
If you want to use real names, get permission. If they don't give permission just use a different names and so don't stick the events specifically to a real life person. I don't see how they can object if they're not named and no personal details are divulged. !!!MY 100TH POST!!!
if the op does that, then it will no longer be 'non-fiction'... in a memoir, the author's name and events written about will make it easy enough for others who were party to said events to recognize themselves and for those who know them to figure out who's being referred to, even if names are changed... which is why there are lawsuits brought against authors who did not get people's permission to write about them... if they're public figures, it's another story, but 'ordinary' people have the right to privacy and can sue if that's violated...
