Avatar: The Mistakes of the Avatar is all about how each Avatar makes a mistake that will be fixed by the next generation. It is divided into four fanons which are each divided into 3 books for a total of 12 books and 120 chapters (Am I really typing this?)
Avatar: Kyoshi's Saga
In the first fanon we find out about Avatar Kyoshi. She made many mistakes. Her most prominent mistake was creating the Dai Li. They would become corrupt and cause problems for Team Avatar Aang. She is one of the oldest Avatars and spent the most amount of time training. She has always had trouble bending big items thus causing her age to be prolonged so that she could more easily learn bending.
Avatar: The Instigator's Friend
In our next fanon we find out about Avatar Roku. While Avatar Kyoshi's mistakes had no effect on Avatar Roku he made even more bigger mistakes. After seeing all the different cultures around the world, he doesn't want to take Sozin's life. If he had, then the War would have been prevented...
Avatar: The Last Airbender
In this fanon we meet Aang. He will solve all the problems of the world created by Kyoshi and Roku, but still create more for Korra. Having the same problem that Roku had he will choose to take away a person's bending rather than kill them. Unfortunately this causes problems in Republic City 40 years after the incident.
Avatar: Legend of Korra
This is the last of the four fanons. This fanon deals with Avatar Korra solving Aang's problems and concluding the saga of mistakes by dealing with Amon.
"Nice chapter, but I agree with Kyoshidude below. Also, make sure to put punctuation at the end of dialogue. And I liked the "five-flame" hotel thing. Nice one!"