In mid-America, researchers find family values holding strong; Middletown Families: Fifty Years of Change and Continuity, by Theodore Caplow and Howard M. Bahr, Bruce A. Chadwick, Reuben Hill, Margaret Holmes Williamson. Minneapolis: University of Minnesota Press. 426 pp. $16.95. Hometown, by Peter Davis. New York: Simon & Schuster. 331 pp. $14.95.

How does Middletown, America, stack up these many years after Robert and Helen Lynd found so much social change there in the 1920s? Surprise! For all the continued air of change in the nation and the world, there has been more continuity than change in the America represented by Middletown. At least this is what the successors to the Lynds found in relation to family life, the topic of the first volume resulting from a restudy of Middletown in the 1970s.

These scholars conclude that their own successors will not mark the '70s as ''a watershed of change away from the family as we know it.'' Indeed, even the family of the year 2000 will be looked back on as little changed in form and structure and ''more successful, especially for women and children, than the family of today.''

''Middletown Families'' is the documented sociological information to provide perspective on two recent popularized versions of such material:

Public television's ''Middletown'' series produced by Peter Davis and set in the community -- Muncie, Ind. -- which the Lynds dubbed Middletown;

''Hometown,'' a prose narrative approach to continuity and change in another ''middle'' community -- Hamilton, Ohio -- written by the same Peter Davis.

Mr. Davis's book contains some of the rawness that reportedly got excised from public TV. It is hard to suppose it was not included at least partly for shock value. Yet in one ''Hometown'' episode it makes a point about change when even the local newspaper rather explicitly reports the case of a respected teacher under fire on a sex charge. And there is a telling sidelight when a conservative pillar of the community defends the accused's rights. His daughter couldn't imagine him taking the same stand 20 years earlier, but he ''had at last fused his nineteenth-century righteousness with the twentieth century's tolerance for diversity.''

In another case, a murder trial, Mr. Davis wryly notes the persistence of class distinction. The prosecuting and defending attorneys ''repaired together for dinner to the Hamilton City Club, an institution that neither the defendant nor his victim nor anyone in either of their families nor anyone they ever knew or even directly worked for could have gotten into.''

Divisions and the overcoming of divisions constitute only one theme in the book. But they are brilliantly dramatized in a basketball game whose excitements both split the town and draw it together.

Some of the names have been changed, though all the events took place, an author's note says. Lively as his storytelling can be, recognizable as many moments instantly are, ''Hometown'' leaves some of the uneasy feeling of a TV docudrama. What is literally, factually true?

Here is where the flatter, academic style of ''Middletown Families'' is more persuasive. You are warned when a generalization is incompletely supported by statistics. You are told what objections might be raised.The facts are there, allowing debate on interpretation, to be sure, but pinning down the record to surveys of what Middletowners themselves do and say.

A prevailing continuity, yes. A maintenance and even enhancement of family life in the midst of the myth of family decline. A slower pace of modernization and urbanization than when the Lynds observed Middletown a half-century before. A ''generation gap'' no greater than at that time. No retreat into the ''nuclear' family and away from the good old days of the extended family of several generations -- partly because there never were the good old days in that sense, and the nuclear family has always been the American norm. But patterns of kinship outside the home have also always been there, and never stronger than now.

For all the continuities, everybody knows changes have taken place -- but maybe not the first ones that come to mind. The mobile society? The Lynds expected Middletowners to move their homes increasingly often. Instead their moving has decreased. More marriages are happy. Parents spend more time with their children. What both boys and girls want is still more time. And they want it not only from fathers, as in the past, but mothers -- from whom in 1924 they most wanted good cooking and housekeeping.

Meanwhile, the lot of working-class women and business-class women has become somewhat equalized. Laundry machines have been added and household help reduced. This means working-class wives in 1978 spent considerably less time than their great-grandmothers of 1890 in doing laundry -- while business-class wives spent considerably more.

On the other hand the growth of federal money in Middletown has not had much of an equalizing effect. An amazing two-thirds of all income received by Middletown families in 1979 came from the federal treasury. But physicians, landlords, professors, got more than their patients, tenants, students. ''Contrary to the opinion held by most Middletowners, the bulk of this (federal) largesse does not go to the poor, and it does not result in any important redistribution of income.''

Still such post-World War II programs as guaranteed home loans have had an impact. Working-class homes have been catching up to business-class homes. ''The allurement of rising from the working class to the business class is much diminished, as is the fear of falling in the other direction.''

Yet, when it comes to the collective future beyond Middletown, today's residents see that nuclear war, pollution, inflation, scarcity, and are ''more pessimistic than any of their predecessors, back to the first settlers.''

The Middletown families' temptation is to turn inward and cherish the status quo. Their challenge may be to turn outward and use Middletown's strengths to cherish the world.