Gift ideas -- arts, literature, books for children; American church architecture; American Churches, by Roger G. Kennedy. New York: Stewart, Tabori & Chang. 296 pp. $50.

This lavishly illustrated coffeetable volume ''is about religious buildings, '' says author Kennedy, ''but its central idea is that the content, not the container, makes a building religious.'' To develop this theme, there are numerous essays covering various architects, those for whom churches are built, the many forms of worship represented, the nature of religion itself, and much more, including two pages of suggestions for further reading. There are also over 200 photographs, most in color, of churches across the United States, ranging from the humble structures of Colonial times to Philip Johnson's dazzlng post-modern Crystal Cathedral. ''American Churches'' provides an attractive and informative look at ''environments for events of the spirit.''