I've only read the first book (and am not finished) so sorry if this stereotypical (or something)
I don't know if you can tell (or is it more of a feeling?) if someone is from The Night World, Especially if you don't know them that well. but I think I saw a guy, he had this sort of mysterious, unknown presence about him. I also think he's hiding something. I don't know if he's dated. though he Disappeared. and if you believe in love at first sight ( Which I do), I think it's happened.