Shinryuu no Koukeisha is a Japanese novel of 422,038 characters, with 12,694 unique words and 2,036 different kanji. Its difficulty rating on Jiten is hard, 3.2 out of 5. The full vocabulary list ranks all 12,694 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.