Narrator

What did you think of the narrative voice? I was kind of thrown by it sometimes because I couldn't decide whether its tone was consistent. It seemed to veer between semiformal and detached to overly casual and involved. One thing in particular really stood out: its use of slang. For example, when the narrator is talking in the narrator's voice about Millat, it says he "got a lot of pu**y." Isn't that an odd way for the narrator to talk? A character, sure. But the narrator? I've seen this with other authors as well, and it always throws me because it seems like the writer is trying to inject a certain personal, casual tone, trying to lend the narrative voice a kind of hip, young personality or something without committing to an actual embodied creation. It's just a disembodied voice ... Thoughts?