There are 9 as far as I and some others are concerned. Technically there are 10 NPCs, but one of which is... well I think several people would agree they aren't a real NPC at the moment. Which is to say there isn't the same range of interaction to be had. You can talk to this NPC, it has AI behind it, but there is no reason to and that's about all I can say without getting into spoilers.