Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Confessional, Direct, Biased
James cultivates a tone of honest, direct discourse in the Governess's manuscript; in so doing, he works to preserve the fictional frame of the story – remember, we're supposed to believe that this is a real-life manuscript that relates a real-life story. The tone he affects to make this scenario seem possible is extremely straightforward, with a kind of "tell-all" quality to it; we're obviously seeing the events through the highly biased eyes of the Governess. This accomplishes two very important things: first of all, James successfully creates a narrator who is lifelike and emotional; secondly, he constructs a narrator who is untrustworthy and questionable precisely because she is so lifelike.