I sometimes half-jokingly maintain that Moby-Dick was really written as part of an early BOOK-IT [1] reading incentive program to improve literacy among whalers by disguising a novel as a cetological guidebook.

There are entire chapters devoted to the harpooning process, sperm whale anatomy, maritime legal disputes over whale harvesting, etc.

[1] - https://en.wikipedia.org/wiki/Pizza_Hut#Book_It!