The strength and weakness of these extracts from American Heritage magazine, adapted for young readers, is the random nature of the separate pieces which make the ""mosaic"" of our national story. There are stirring pieces on major crises -- and the human interest of such disparate trivia as curlicued Valentines at the turn of the century and the internecine warfare of volunteer fire departments. Three hundred wonderful reproductions and photographs, many in colon are spliced to form a record of sailing ships, of theatrical posters, of stage coach travel, of the building of the Brooklyn Bridge and the lurid drama of the dime novel. Here are Bluebeard, the battle of New Orleans, photographs of Robert E. Lee's sword, Salem's days of sailing glory and the virile camaraderie of mountain men at rendezvous in the Wind River mountains. No one volume can tell the whole American story. This given a strong impressionistic look backward, with an introduction by Bruce Catton.