Pedantic:
An adjective that describes words, phrases, or general tone that is overly, scholarly, academic, or bookish.

Example:
"Some men have been virtuous blindly, others have speculated fantastically, and others have been shrewd to bad purposes; but you, sir, I am sure, will give under your hand, nothing but what is at the same moment wise, practical and good, your account of yourself will show that you are ashamed of no origin; a thing the more important, as you prove, how little necessary all origin is to happiness, virtue, or greatness."
-Autobiography of Benjamin Franklin

Explanation:
The tone and diction of this autobiography is very pedantic. This is because Franklin was a highly regarded, scholarly man. He was expected to have a well educated and well written book. The purpose of this is to show he is indeed scholarly and educated. This is important in this book because he is trying to explain how to live life (his virtues), and if he wasn't intellectual then the reader would not follow his virtues.