Is this mold?

I ordered The Road Goes Ever On and On (9780007312696, the small "map" book from Brian Sibley and John Howe with the red cloth binding and the little pouch in the back with a fold-up map) on eBay, it arrived recently and is in pretty good shape overall, but had this patchy discoloration on the pouch.

Is this mold? Any straightforward way to treat it or should I just junk it? I assume storing one moldy book next to your other books is a good way to end up with more moldy books.