FunkyD all books but 4 have both rotes complete, the last one the love route is still in the works and is completelly different than the slave route (the others have differences but the setting is the same).
the main difference is when they are chosen.
In Book 1 it is chosen when talking with Katara, Slave Route asks for rewards for helping and Love does not. The game itself does not have that much changes.
In Book 2 it is chosen right before the route starts. You control different characters, and while many things are the same this change will affect interactions, slowly at first but more and more as the book progreses.
In book 3 (you are here), it takes some time before you can choose the routes. After a while you will enter an underground dungeon and meet the obvious book antagonist. He will make you an offer. Accept for Slave, reject for Love. After that the story goes at a big change in direction though, despite most mechanics staying the same.
In book 4 your choice is again right away, and again because of different characters, but it also changes the setting. In Slave Route you are in Korra's Book 1, and in Love Route, still being worked on, you are in Korra's Book 3, in another location, with other mechanics and either new characters or they are behaving in very different ways due to the time between the timelines.
