I know I've said this before, but the Kink books and watching SM porn should give plus or minus 5 KP like the GP related ones do. Also, the spank option should award points up to 50 so you can then transition right into head pats for points up to 100. That would mean you would only have to buy books for 0-10, then you could organically raise the points using actions and dates without having to waste a lot of money on the books.
BTW the spank option seems to be buggy. It's supposed to keep adding KP up to 40, but it doesn't seem to work for every girl past 30 or maybe I'm just doing it too often. I try to do it every day at the same time, but it doesn't always work.
Also btw, NOT every girl has a talk option to raise or lower KP and this should definitely be addressed. Kleio for sure doesn't have one and it makes getting her KP high enough for the Pixie Harem really difficult. Morgan's KP talk option also stops working at a certain point. I'm not sure if it's related to her masculinity stat or her KP stat, but at some point the sex talk option stops adding KP. Not sure if this is a bug or intentional.