Hybrid bookstore honto has ranked the manga and light novels that are being adapted into anime scheduled for broadcast starting around October 2020. The titles were ranked according to the total number of purchased books from bookstores like honto’s own, Maruzen, Junkudo, Bunkyodo, and others, from 1 April 2020 to 6 September 2020. They collected data on the readership as well.
Haikyuu!! (43 volumes) tops the list, followed by Golden Kamuy (22 volumes), Jujutsu Kaisen (11 volumes), and Moriarty the Patriot (12 volumes) (the full list of the top 10 is at the end of this post).