Can't believe I haven't reviewed this yet. This is one of, if not the MOST ambitious, true-to-life, accurate 18+ fan interpretation of the Universe it's based on. However, in order to break down the game accurately, let's review the game based by Book and what we have so far. (For those of you who hate walls of text, there is a TLDR at the bottom):
Book 1: Water (4/5)
This book is fairly straightforward. You play as Aang, or more accurately a possessed version of Aang, out to get that sweet water tribe pussy. The story here essentially covers the time he spends in the South Pole prior to his leaving for the Ba Sing Se. Essentially you get to train Katara to be your personal slut, or get her to love you enough to spread her legs for you. The dialogue is hilarious, witty, and full of charm. The sex scenes are great and the characters are painfully in line with their actual personalities in the series. My only gripe is that we didn't get to fuck Nami, and the most we can go is a blowjob. Also, the slave route with Katara wasn't as convincing as the love route. Other than that, it's a very strong start to this series.
Book 2: Fire (5/5)
This is without a doubt, the best-written book in my opinion. It has the best dialogue, ALL the characters are interesting and accurate as F and you can actually imagine the original voice actors voicing those lines and not seem out of place (barring the sex jokes and F words of course) and Both slave and love routes are equally compelling and well-written. You play either as Prince Zuko, or a random thief who got caught infiltrating the palace. I don't want to spoil too much about this chapter and leave it to you to judge, but it is undoubtedly to me, one of the best-written fanfics to exist in the media of 18+ parodies. Mai, I fucking love you.
Book 3: Earth (4/5)
A pretty decent chapter covering your time in Ba Sing Se, and training your Earthbending with Toph. You play as Aang once again and you're in for a great time if you're into Lolis. Not too much to say about this chapter, it's similar to Book 1 in terms of quality. Great sex scenes, and a decent story. It also similarly suffers the same problem as Book 1 where the slave route isn't particularly convincing, but it at least has a slew of new side characters to stick your tip in (Smellerbee and Suki for the win!) Another solid endeavor that will get you going.
Book 4: The Legend of Korra (3 and a half/5)
Since this book is incomplete, I won't gripe too much or give a solid rating just yet. It's decent, but once again the slave route suffers the same fate as two of the previous chapters. As much as I love seeing Korra humiliated like the little cunt she is, it didn't feel very organic or realistic the way she becomes a sex-hungry whore. I did, however, love the way she slowly breaks down and becomes more vulnerable and much less confident in herself over the duration of the training. Being in the role of Tenzin though may be a bit of an issue (especially with the while Jinora thing, which is thankfully optional).
Normally, I don't mind incest, especially in fan-fiction, but the way this one was written just made me a bit too uncomfortable and pushes a few more boundaries than I'm used to. Essentially, its still a great chapter so far, and if you have the guts or the lack of inhibitions for it, go right ahead, You'll enjoy it much more than I did. I will say however, that the Love route is looking VERY promising so far, and the context of being in the shoes of a fellow patient in recovery slowly building a friendship with a bitter and discouraged Korra is probably the best way to go. I have high hopes for this route and if their previous books were any indication, it will probably end well.
TLDR; A very well-written novel that connects itself to the universe it's based on almost seamlessly and brings the characters to life in a convincing and realistic manner (most of the time). Great dialogue, funny lines, and witty writing really keep this in the running. It has very well-illustrated sex scenes and decent animations to help it along and I will wait as long as necessary for it to be completed.
Final Rating: 4 and a half stars (5 stars since that option doesn't exist. Why? Not enough Sokka. Shame on you Mity. XD)