I remember discovering this game 3 years ago while I was new to Ren'Py adult games, when Book 3's slave route was still in development. I remember liking the game so much that I played the game several hours straight. While I still like it enough that I come back to it, that rate has been growing less and less.
In general, there are four books, which are basically chapters between different time periods in the ATLA lore. Each book since the first has a "Love" and "Slave" route, with the Love routes being developed after the completion of the slave route. The newer content has better art and animation, which you can compare with the five year gap between Book 1 and the latest scenes in Book 4. Each book has you linearly progress in interacting with a main girl and a few canon and non-canon side girls.
Been a long time since I played Book 1 and I remember it being straight forward and short compared to the next books. It was pretty vanilla though with the sex scenes, which I appreciate. Probably decent for 2016, but not for a game in 2021. In my opinion, the game peaks in Book 2. It is still a mostly linear experience, but the story could branch out a bit and both routes have multiple endings. It is also when the game first introduces an attempt in animating the sex scenes, which wasn't smooth with just a few frames, but worked decently enough in my opinion. My personal favorite is the love route, and I still think the writing on the main story is really good and the best one in the game. The writing made me invested to the main girls as characters and the actual story itself.
After that the writing on the next two books didn’t feel as great, so I’d skip through the dialogue most of the time. I still liked Book 3's slave route where progressing was still straight forward and consistent. Somewhere in the middle Book 3's love route was when I started getting annoyed at the game. The humor, which was always a large part of the game and juvenile but initially funny with few misses, felt even cheaper and sometimes make the protagonist be an unlikeable douchebag. The flow of the game would feel inconsistent sometimes and the newer minigames being added felt needless. The length feels even longer with even more sex scenes. However many of these scenes, especially the unavoidable ones, felt they were included just for the sake of it instead of being properly written in. This also includes some new fetishes, which felt tokenly added in and some can’t be avoided. For both Book 3 routes, the game went back to being more linear, not including multiple endings like in the second book. These flaws would continue and in my opinion be way worse in Book 4, although I have a slight soft spot for the still developing love route. To sum it up, I just didn't like the direction the writing of the game was taking.
Maybe I just have high expectations ever since playing through Book 2, but I felt the potential of the game’s story writing was very much wasted after that. The sex scenes are still good, but it says much about the game if I’m becoming more inclined to use the gallery mod instead of playing through properly.