SAD RIDDANCE Less than 13 years after baseball's most joyous marriage was consummated, it ended in 1965 with the sport's most acrimonious divorce, as a team, a city, a country and a baseball industry ripped themselves from their moorings.   The Milwaukee Braves' accomplishments from 1953-59 were collectively hailed as the "Miracle of Milwaukee," and geographically and economically altered the landscape of major league baseball forever. Then the miracle became a mirage. Attendance plummeted, the team declined, and new ownership bought the franchise with the cynical and ill-concealed intent of moving it to Atlanta.   "Sad Riddance" describes the betrothal and the betrayal of Milwaukee by major league baseball, and explores how two entities that in 1965 were about to disappear forever - the "Happy Days" Milwaukee and the once-adored Milwaukee Braves - bade farewell to each other amid the most heated pennant race the National League had experienced in almost 60 years, at a time when the 10 NL teams had a total of 29 future Hall of Famers.  The book also examines in detail multiple factors that led to the Braves' record-breaking success in the 1950s, along with the lesser-known elements that contributed to their decline and eventual departure, and the emotions - then and now - felt in 1965 by young people who had believed that the Milwaukee Braves were their birthrights.