Question: In what year was Robert M. Pirsig's most famous book first published?

<P0-S0> Robert Maynard Pirsig (September 6, 1928 – April 24, 2017) was an American writer and philosopher. <P0-S1>  He was the author of the philosophical novels "Zen and the Art of Motorcycle Maintenance: An Inquiry into Values" (1974) and "" (1991). <SEP> <P1-S0> The German Shepherd Dog in Word and Picture is a book first published in 1923. <P1-S1>  The book is a revised translation from German into English of Der deutsche Schäferhund in Wort und Bild which was written by Max von Stephanitz (the founder of the German Shepherd Dog breed) and first published in 1901 as a 72-page booklet (plus 24 pages of advertising). <P1-S2>  Der deutsche Schäferhund in Wort und Bild was subsequently expanded with later editions, and a complete makeover was published in 1921 with the sixth edition. <P1-S3>  A seventh edition of the German book was published in the same year as the first editions in English, 1923. <SEP> <P2-S0> Samors has authored, co-authored and/or published twenty five books about Chicago's neighborhoods, downtown, Michigan Avenue, the Chicago River, Lake Shore Drive, and Chicago's airports, and in addition has written and published nostalgic books about growing up in Chicago in the eras of the 1930s, 1940s, 1950s, and 1960s. <P2-S1>  His book, co-authored with Michael Williams, "The Old Chicago Neighborhood: Remembering Chicago in the 1940s", won the 2003 Independent Publisher Book Award first place award in history, his book "Chicago in the Sixties: Remembering a Time of Change" won the 2007 Independent Publisher Book first place award in history, his book, "Downtown Chicago in Transition", co-authored with Eric Bronsky, won the 2008 Independent Publisher Book second place award for Midwest Region books, and his book, "The Rise of The Magnificent Mile," (co-authored with Eric Bronsky), won the 2009 Independent Publisher Book first place award in the Great Lakes region. <P2-S2>  He co-authored and published three new books in 2008, including "Clark Weber's Rock and Roll Radio", by Clark Weber, "Never Put Ketchup On A Hot Dog", by Bob Schwartz, and "The Rise of the Magnificent Mile", co-authored with Eric Bronsky. <P2-S3>  In 2010, he published and/or co-authored, with Tony Macaluso and Julia S. Bachrach, "Sounds of Chicago's Lakefront: A Celebration of the Grant Park Music Festival, "A Kid From The Windy City," co-authored by Lee B. Stern and Neal Samors, and "Paths Through The Wilderness: American Indian Trail Marker Trees" by Dennis Downes, with Neal Samors. <P2-S4>  Next, he was the publisher and co-author of "Chicago's Lake Shore Drive: Urban America's Most Beautiful Roadway" and served as publisher of "Chicago From The Sky: A Region Transformed" by Lawrence Okrent. <P2-S5>  In 2011, he published and co-authored, "Chicago's Classic Restaurants: Past, Present and Future" with Eric Bronsky and Robert Dauber, in 2013 he published and co-authored "Chicago's River At Work And At Play" with Steven Dahlman, and, in 2015, he published and co-authored "Now Arriving: Traveling To And From Chicago By Air, 90 Years of Flight" with Christopher Lynch. <P2-S6>  Dr. Samors publishes books through his company, Chicago's Books Press, an imprint of Chicago's Neighborhoods, Inc. <P2-S7>  He has a PhD and MALS from Northwestern University, an MA from Northern Illinois University and a BA from the University of Wisconsin–Madison. <P2-S8>  In 2010, Dr. Samors was selected as a Prominent Alumnus by the Sullivan High School Alumni Association. <SEP> <P3-S0> Zen and the Art of Motorcycle Maintenance: An Inquiry into Values (ZAMM), by Robert M. Pirsig, is a book that was first published in 1974. <P3-S1>  It is a work of fictionalized autobiography, and is the first of Pirsig's texts in which he explores his Metaphysics of Quality.