Given that it's called '50 new true stories', it's most likely a non - fiction genre. It might be in the category of nature - related non - fiction if the 'moth' is a key part of the stories, or it could be a more general collection of human - interest true stories that just happen to use moths as a unifying theme.
It could be non - fiction, since it mentions 'true stories'.
Since the title contains 'true stories', it is likely to be non - fiction. However, depending on how the stories are told, it could also have elements of memoir if the narrators are sharing their personal experiences related to moths and these wonders. It might also be considered a form of nature writing if it focuses on the scientific or ecological aspects of moths. If there are strong emotional elements in the stories, it could even be a bit of a hybrid between non - fiction and literary non - fiction.