From the Edward Abbey website:
The Dream Garden Press edition of The Monkey Wrench Gang issued in the Spring of 1985, with illustrations by Robert Crumb, was an immediate success and the first edition of 5,000 copies sold out. A second printing came out in the fall of 1985 and at that time Ken Sanders asked Crumb to do some additional MWG artwork including a color cover for publication in a Monkey Wrench Gang Calendar.
In 1986, the 1987 Monkey Wrench Gang Calendar was published and was a complete disaster. It didn't sell and most of the copies were later sent to the paper recyclers. Ken lost almost $20,000 on that fiasco. Needless to say it didn't become an annual calendar like the Edward Abbey Western Wilderness Calendar.
The tenth anniversary edition of the classic eco-terrorist novel added 7 full-page and 32 text illustrations by Robert Crumb. This calendar includes all those Crumb drawings--plus five new drawing created especially for this calendar. In total, there are 14 full-page color illustrations and 4 smaller color illustrations and 39 black & white illustrations.