Sagas of today's South; Shiloh and Other Stories, by Bobbie Ann Mason. New York: Harper & Row. 247 pp.

This is a collection of stories about '80s life in the South. Most of the people in them live near Paducah, Kentucky. Nearly all are country people, confronting what this reader had naively thought of as the problems of the city. Families break up; people are out of work; and the famous Southern ''sense of place'' gets frayed when old people sell their farms and furniture and move to town.

In these stories, told in a straightforward way that notices the rattle of Granny's false teeth but also makes you love Granny, the characters muse and comment on the changes in their lives. The way they think is unique, funny, and flavored with the salt of the earth.

One woman, thinking about remarrying, wonders if a stepfather for her daughter, a 10-year-old vegetarian who makes cynical remarks about her mother's eating habits, would be like a sugar substitute - not quite real.

A man who was injured when his truck jackknifed sits home making models, while his wife works and gets interested in body building. They are drifting apart, but his interest in models has made him want to build her a log cabin. When she says she is leaving him, he feels that ''he'll have to think of something else, quickly.''

A man whose daughter is away at college has been struggling through ''The Encyclopedia of Philosophy'' to keep up with her, only to discover she is taking physics, not philosophy.

Mass culture bumps into these peoples' lives by way of television, sickness, children returning from college, and the changing life styles of neighbors and relatives.

It seems the more jolting because in Bobbie Ann Mason's intimate pictures of her characters there is always a sense of the old way of doing things - in their memories, or in the remarks of grandparents, who are nearly always present.

You come to know the characters so well that you know just how the next collision with modern life is going to feel. Some characters are suffering from or afraid of illness, and on one level the descriptions of their quandaries are disturbing.

But on another they are inspiring. Mason characters are honest, unpretentious people who don't have terrific victories over their problems, but nonetheless face them with level heads.

Their lives change, but they stay themselves. The feeling you get from them is that life has never been easy, but they are going to keep at it, with a spirit that's gritty, funny, and refreshing at the same time.