Cable TV sports -- and book authors on videotape

TV notes: * TV sports fans will have a welcome, if expensive, cable surprise starting later in the year. TSN (The Sports Network), cable TV's first multiregional pay television sports service, has announced that it will present more than 500 events a year to at least five regions across the country, with at least ten more regions eventually following suite.

Professional sports franchises such as the Baltimore Orioles baseball, Chicago Black Hawks hockey, Chicago Sting soccer, Chicago White Sox baseball, Chicago Bulls basketball, Detroit Tigers, Milwaukee Brewers, Milwaukee Bucks, and Seattle Supersonics have already joined forces with Group W Satellite Communications to form the regional sports network.

* Some of America's favorite book authors are taking to videotape in what seems to be an act of self-preservation. Broadway Video is underwriting a series of videotaped Readings produced by Elia Katz and now available to libraries, schools, community organizations and television stations around the country. Already Joyce Carol Oates, John Irving, Bruce Jay Friedman, and Isaac Bashevis Singer have taped readings of their most celebrated works. Producer Katz, who admits paying the authors only ''an honorarium'' for their work, says: ''I believe we are currently in a golden age of American literature . . . yet, ironically, books themselves are selling fewer and fewer copies. We hope these readings will help generate a much wider public interest in books . . . reach out to a generation raised on television in an era of shrinking literacy.'' ''Reading Rainbow'' on PBS these days is also trying to use TV to increase interest in reading.