Casey Stengel once tried to define to a TV audience the appeal of his New York Mets and their fans: ""I wannasay that the Mets fans has been marvelous. And they come out and done better than we have on the field and I'm glad we got 'em. If we could do as well as them it'd be better...I'm glad to see that we got so many of the ladies turnin' out to see our team 'cause it proves that we got effeminate appeal which is the result of my charm school which I run as chief instructor in effeminate appeal and we got 'em turnin' out with their dates, the young 'uns and the old 'uns, and I wish we could do it better on the field."" ...Yes, the Mets are the team of the common people. Their fans participate in their team's errors at Shea Stadium with a delight unknown to the chi-chi, uptown, touristy spectators at Yankee Stadium. Lindsey Nelson has been announcing for the team from its beginning. His book is a charming example of modesty and light wit in a field more often strewn with box-office figures, salaries and playing records. ""Are you going to work on fly balls?"" Casey was asked. ""They don't bother us none, "" he said. ""We're still working on grounders.