Doubleday: 177 pp.; $4.95; paperback $1.95

THE LOOP GAROO KID says a novel can be anything it wants to be: a vaudeville show, the six o'clock news, the mumbling of wild men saddled by demons. That's a good thing to remember when you're reading Yellow Back Radio Broke-Down. because it will save you the trouble of having to come to that conclusion on your own and then wondering where to go from there. The book is a junkyard for the left-over bits and pieces of American myths that couldn't quite be worked into The System; interesting how you often learn more about people from the stuff they throw away than from what they admit to keeping. Ishmael Reed has taken assorted scraps and shavings from American history, religion, and polities and made of them a tale that at first sounds like a child's nightmare of shadows and misconceptions. But by the time you finish, it's no longer so childish.

It's all about the Loop Garoo Kid, a black cowboy of demonic origins, who in the beginning is traveling with a small circus destined for the Old West town of Yellow Back Radio. When the circus gets there, it is met by a band of loving children who have succeeded in driving out the resident adults in order to "create their own fiction." But the misbegotten villain, greedy rancher Drag Gibson, slaughters the children and most of the circus, leaving only Loop Garoo to plot a spectacular revenge, complete with show-downs, hide-outs. Christ figures, and all the working magic of the American Hoo-Doo Church.

Horse opera. Clever don't you think? And the Hoo-Doo cult of North America. A much richer art form than preaching to fishermen and riding into town on the back of an ass. And that apotheosis. How disgusting. He had such an ego. "I'm the Son of God." ... And his method had no style at all. Compare his cheap performance at the grave-site of Lot-sickening- and that parable of our friend Buddha and the mustard seed. One, just a grandstand exhibition, and the other, beautiful, artistic and profound. The pieces are laid out for you to put together- and the author lets you know from the beginning that what you come up with is your problem, not his.

WHICH WOULD be fine if the book meekly promised to make its points according to some set up we've all seen before. A hip sermon maybe, railing against whatever the author feels up to taking on, or a straight allegory with an easy one-to-one correspondence between the symbols and what they represent, or even a clever satire with the edge precisely sharpened on some well-turned witticisms. But in this book, you never know what's going to come up next. One minute you're riding along, pleased with yourself for having figured out the subtleties hidden in some scene, and the next page you're hit in the face with a four-letter explanation. The characters don't even manage to stay pinned down. Drag Gibson is a primary colored capitalist- but suddenly he's doing things that scream Chicago in your ear. These things could make for a very annoying novel, creating blind paths that lead to nowhere, a riot just for the hell of it. Instead, however, you wind up with a strong, funny book that manages to make its own kind of sense. It works the way a poker game does, depending entirely on the player's tricks, timing, and style. The author of this tale has got all three.

I don't know much about Ishmael Reed, but from reading his book. I imagine he'd make an incredibly good drunk. His writing is like that, sky high and reeling along, everything just enough out of focus so that you get the feeling he's tilted the whole world a few degrees his way and he's letting you in on what he sees. What you see and what you don't is up to your imagination. Reed has a lot to say about what he thinks this country has been up to in the past 200 years. but he isn't doing any preaching. He has this way of looking at things that lets you go on where he left off, if you want to- but if you'd rather spend the entire book in the Rapid Black Cougar Saloon (such a fine name) watching Mustache Sal do her thing with the cowhands, that's okay with him, too.

IT'S A ROUGHSHOD book, and it probably won't get to you much unless the back of your mind happens to resemble Reed's. He's having a good time taking a look at the same things CBS documentaries look at, without the pain of having to take it seriously. You'll find your own way of dealing with the book, but try not to think too hard about what he's got to say; enjoy the images he puts you on to, and the pictures that get conjured up in your head. You'll like it a lot more that way, and the message, with the inevitability of Ishmael Reed's hangover, will come later.