Every year four urbanized black bears make the journey from San Francisco to Yosemite. Known as Bruinhilda, Alphonse, Franklin, and Floyd, this quartet regularly creates mischief in Yosemite Valley and beyond. This collection of nearly 300 hilarious strips originally appeared in the San Francisco Chronicle between 1999 and 2004.
Not really nonfiction, but that's closer than anything else. A collection of daily strips of the comic "Farley", all having something related (sometimes very loosely ;) to Yosemite.