John Cage is our first and best all-American dadaist, a genuine kook, an I Ching addict, Zen dancer, mushroom specialist, the undisputed master of non-music, the ""prepared piano,"" the four minutes and thirty-three seconds of Mallarmean silence before the keyboard, the Beethoven of the Twelve Radios flipping from one dial to the next in a supreme collagist cacophony, the granddaddy of ""artistic"" indeterminacy, the meaningless gesture, electric hellzapoppin, and, of course, ""happenings,"" which he has now rejected. From a recent interview: ""When I hear the word 'happenings' I spew wildly into my lunch."" Mary McCarthy has called him a sour utopian, a pregnant phrase Marshall McLuhan will no doubt decode. A Year from Monday, another batch of theoretical musings and esoteric quips, following on the heels of Silence and the notes to his Retrospective Concert, should also be decoded, perhaps by the Beatles and Susan Sontag. Is Cage a genius? One has the feeling while reading these wonderfully idiosyncratic ""lectures,"" ""essays"" on Miro or Schoenberg or Duchamp, and the two-part DIARY: HOW TO IMPROVE THE WORLD (YOU WILL ONLY MAKE MATTERS WORSE), that the thought has now and then crossed his mind. Certainly he is a humorist, and his prose style is the finest since Gertrude Stein. An ideal gift book.