Ikiteiku Tame no Classic is a Japanese non-fiction of 114,040 characters, with 6,604 unique words and 1,616 different kanji. Its difficulty rating on Jiten is hard, 3.8 out of 5. The full vocabulary list ranks all 6,604 words by how often they appear, and you can study them on Jiten or download them as an Anki deck.
Here are some of the words that appear most often in this media, as well as a sample of its rarer vocabulary.