TV's new mystery lady: Jessica Fletcher

Angela Lansbury has given Miss Marple the Glamour magazine ''Make-Over'' treatment. In her first television series, Murder, She Wrote (CBS, Sunday, Sept. 30, 8- 10 p.m.; thereafter Sundays, 8-9 p.m.), Angela Lansbury plays Jessica Fletcher, an attractive widow living in Cabot Cove, Maine, who has just begun to write mystery novels. There's a bit of a well-manicured-and-coiffed Miss Marple in her , as well as a touch of Agatha Christie. Add more than a hint of Auntie Mame, and you have a refreshing new television personality.

The premiere episode is a bit too long on plot, however, and too short on characterization. I would have liked to learn more of Jessica's life in Cabot Cove before she was sent out into the complex world of New York City publishing society and its chic suburbs to solve a murder in which her nephew is inexplicably implicated. The story line has a lot of inexplicables. But who's quibbling?

I admit that somehow Jessica seems just a bit too slick and sophisticated - I miss the more idiosyncratic character of Miss Marple. But I'll take Jessica as is, if necessary, just as long as I can count on Angela Lansbury on TV every Sunday, right after ''60 Minutes.''

''We think you're just sensational, Mame ... ''