When are four stories only one? What is black and white but really is not black and white?

Answers to these and numerous other puzzles can be found in the most recent Caldecott Award Winner, BLACK AND WHITE by David Macaulay (Houghton, Mifflin, 1990. $14.95). Clues and riddles run rampant in this new picture book, which was recently named by the American Library Association as the best book of the year.An early tip-off to the writer's novel approach can be found in the frontispiece showing broken prison bars and a knotted escape rope with the author's name spilling down the page. The warning: "This book appears to contain a number of stories that do not necessarily occur at the same time. Then again, it maybe contains only one story. In any event, careful inspection of both words and pictures is recommended."

Perhaps this warning is an invitation that the artist has broken "out of bonds" of traditional picture books and reached into a bag of tricks to tell a unique tale. Or is it four tales?

First, the book is not printed in black and white. The title on the cover is white, green and blue on a black background. The pictures within are full-color. This alone warns the reader not to expect anything as simple as that.

The internal format of double-page spreads is divided into four frames, and in each a different story unfolds. In an inventive twist, similar characters suddenly appear in more than one vignette as themes, events and time tables become interchanged. For example, a boy riding alone on a train has a visitor who resembles an escaped convict from another story, who has hidden among Holstein cows. The cows have wandered onto the tracks that hold up the train for which commuters are waiting in a third story. As the passengers wait for the delayed train, they make newspaper costumes and shred paper into snow, which is directly related to the fourth story.

Reading back and forth, checking clues and seeking similarities make this an adventure to enjoy and puzzle over but never really solve. And nailing down answers by spending more time in the pursuit doesn't help at all. On the contrary, it just seems to open up more options. Now that is a real mind teaser!

Macaulay's work has always been an adventure. "Castle," "Underground," "Cathedral" and the other six architectural books have taken readers of all ages to times and places in history. "The Way Things Work," a whopping manual of the intricacies of the inner-workings of machines is a best seller for both young and adult readers. "Baaa" and "Why the Chicken Crossed the Road" are combinations of political commentary and tongue-in-cheek humor. All of Macaulay's works have been translated into a dozen languages with countless awards.

It is said of "Black and White" that "play is the wellspring of creativity, and Macaulay is playing with the form itself . . . . " There is no denying that this author is a master of play. He has delighted readers of all ages for years. The Caldecott Award is well deserved.