If I ruled the world, or at least a publishing company, all books would contain as much supplementary information as possible. Nonfiction, fiction—doesn’t matter. Every work would have an appendix filled with diagrams, background information, digressions and anecdata. And of course, maps. Lots and lots of maps
Victoria Johnson, “The Maps We Wandered Into As Kids” (cf. my post, “Maps of Fictional Worlds”)