Morality chains is rather good read, all considered. It largely follows Azulas and Zukos journey through life, with regular flashback to their childhood illuminating why either sibling behave they way they do in a rather pointed fashion.
Interestingly, it nearly totally disregards the happenings and travails of the Gaang. It's not that they don't happen, they're just offscreen events. The focus is really
on the siblings, their thoughts and reasonings, as well as their actions.
A slight minus, though: it is bit on the bad side of spelling, if you have an eye for that (mostly homonyms and typos forming otherwise correct words).
(most recent chapter: 24)