What is the author's style in The Tell-Tale Heart by Edgar Allan Poe?

Poe uses language; in this case the narrator's way of speaking, to expose his insanity. Even from the very first line, he sets up the narrator's speaking patterns as those of a man fettered with nervous agitation:

"True! - nervous - very, very dreadfully nervous I had been and am; but why will you say that I am mad?" (pg. 13)