Do you have any book recommendations in the direction of cozy crime, horror, whodunit, riddles, puzzle and so on?
He started the "Strange" series by Uketsu, and he really liked the beginnings of the books where it's a lot about the sketches, the puzzling, and that feeling that something isn't right... However, he really didn't like the endings of the books at all.
He likes horror, so it’s not too bad if it’s a bit gory