I'm not surprised by this release though I wonder if it is a little to early in the game's development to release.
Yeah, I agree that it's a little weird, and a bit early. I mean, there are VERY few books out for that system right now. If you exclude simple play-assistance products (GM screen, cards, etc.) and the 100% redundant (and pointless IMO) player's handbook, there is really only 1 core book, a couple of "magic item" books, and a couple of adventures. Adding a "sex" book when there are nearly no other options is going to color your brand pretty strongly. I mean, shouldn't they concentrate on getting the bestiary out, and maybe a few more other options that would be helpful for a wide range of gamers (settings, religions, more detail on specific regions, etc.) before diving into something that is a niche at best?
This is assuming that it also doesn't get turned into a weird bunch of sexist soft core whatever, which is something this hobby can have a tough time distinguishing itself from (rightfully so, given some of the issues in the past across a wide spectrum of games). I don't know any of the names involved so I won't guess what will happen one way or the other, but the core book itself has one or two examples of weirdness in this direction already, so it is definitely an uphill battle.
I guess ultimately it just begs the question: is this REALLY the direction you want to go right now? And can you convince consumers that you're doing it for some reason other than cheap reaction marketing?