The edges will be slightly worn and perhaps soiled. It always makes sense to keep any work on paper out of direct sunlight and use UV filtering glas. Check periodically for signs of foxing or mold, as that is one of the common problems with paper and high humidity. It comes in various forms including sheets. No single book tells everything there is to know about map collecting.
Libraries often have books on cartography and some are offered by large book dealers or map dealers.
Some reference books are offered on this Web site . Many reference books are rare and seldom are on the market. Since they each have a different emphasis their value varies. Most larger dealers issue catalogs of material. There are often well documented and useful.