Book collecting isn't always just about having a valuable book. Owning some books is like owning a piece of history.
Edward Abbey's The Monkey Wrench Gang is a perfect example of such a book. It literally started a radical environmental movement (with some help from another of Abbey's books) and inspired the common phrase, "throws a monkey wrench into the works." It's part of America's culture, regardless of how you feel about the subject matter.
Because it's a relatively modern book, identifying a first edition is easy. Simply check the printing details on the copyright page - if it was printed in 1975 and is labeled as a first edition (with no "second printing" or similar modifier afterwards), it's a first edition.
A remaindered first edition in very fine condition with the map endpapers intact sold last year for $300. A signed first edition in about fine condition sold back in 2007 for $780, nearly matching the auction house's maximum appraisal at the time. Some booksellers now list signed first editions for $1,000 or more, making it quite a find.