Having finished the Book 3's slave route, I have to say that I'm amazed. It is nothing short out of outstanding that Book 3's slave route alone has more sex scenes than Magic Shop, Witch Trainer and Star Channel 34 combined. And not just the scenes, but also the girls as well, which amount to about 11, a great improvement over the 5 that were available in Book 2.
Though now this makes me wonder if all or even most of these girls are going to be available in the coming love route, since you fucked a lot of them via hypnosis, which was a recurring mechanic during this route. Something as rapey as that would be a little weird in the love route, more so because the choice that branches the routes was allying yourself with Long Feng to learn his hypnosis teachings.
One thing though that I have to criticize of this Book is the fucking obsidian, finding most of them is not that hard, but there is an specific one that can be a little tricky. If you happen to finish the "Kill the Avatar" quest while there are other quests remaining, you will be locked out of them, the game saying you completed them all. The game never gives you any hint this is gonna happen, which is a problem because there are 2 quests that reward you obsidian. I had progressed a lot since my previous save so I had to use console commands to give me the last obsidian I needed. Not the worst thing thing to happen in a porn game ever, but it was still an annoyance.