I do not mean "to go all ...'Literary Critic" on the author, but....."
Actually, I do mean to go all Literary Critic on the author. His ignorance is clearly in evidence and his writing is simply bad writing. Of course, we might consider he is a very capable author, who intends to show how ignorant his character is. That is always possible.
It may be that in the book you read, the character is one of those people who use all manner of slang expressions, because his level of education is limited and he simply speaks, generally, like an idiot. In that case, we can have a good laugh at the matter.