A personal favorite, the WORLD OF GREYHAWK box set [Gary Gygax, 1983] for AD&D is a feast for the eyes. The draw of the set is, of course, the gorgeous two-piece map of the eastern extents of the continent of Oerik.
The maps are truly massive: The two sourcebooks in the set [Guide to the World of Greyhawk (80 pages) & Glossography (48 pages)], I’ve placed them on the maps put their dimensions in perspective.
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Was the cover style of D&D 3e inspired by the World of Greyhawk box art?