Robert Wilson likes to be formal and precise about the dreamlike mysteries he shares with his audience.

So the program for ''The Knee Plays,'' his latest production at the American Repertory Theatre (ART) here, offers a step-by-step outline of the action. Before the lights go down for the first scene, you know the evening will begin with a man reading a book in a tree while a lion crouches underneath, and finish with a tree growing from a book in a library and that the characters will range from a famous admiral to an anonymous Japanese basket-seller.

On paper, the show sounds like quite an epic, with settings as diverse as a tropical jungle, the bottom of a sea, and the United States during the Civil War.

What you can't learn from perusing the program is how ingeniously director Wilson makes the epic come to life, not using elaborate tricks and illusions, but drawing on a small bundle of elegant stage effects with roots in traditional Japanese theater as well as his own imagination. For all its exotic locations and events, ''The Knee Plays'' is one of Wilson's more modest concoctions, depending less on size and spectacle than on simplicity and transparency, qualities that shine through almost every moment of the splendid new production of the work that runs through Oct. 5 at the ART and then begins a national tour.

"The Knee Plays" has a history that's as unusual as its name. It began when Wilson decided to assemble a massive international production, called ''the CIVIL warS: a tree is best measured when it is down,'' to be performed at the Olympic Arts Festival in Los Angeles two years ago. Portions of the show were developed and staged in countries around the world and were to have come together in California for a limited number of marathon performances lasting some 10 hours. Although these never took place for financial reasons, the complete ''CIVIL warS'' was nominated for the Pulitzer Prize in drama this year, which it did not receive, possibly because the entire show was never actually produced as intended.