BLUE HIGHWAYS: A JOURNEY INTO AMERICA. By William Least Heat Moon. Illustrated. 420 pages. An Atlan- tic Monthly Press Book: Little, Brown and Company. $17.50.
SOME men, when they lose their jobs and their wives, take to drink and go to the dogs. When William Least Heat Moon lost his, he took to the road and went to Subtle, Neon, and Mouthcard, Ky.; to Dull, Weakly, and Only, Tenn.; to Dime Box, Tex., Scratch Ankle, Ala., and Gnawbone, Ind. He wrote a book about his travels in order to find out where he was trying to arrive at and called it ''Blue Highways,'' because on old maps the back roads were colored in blue. The book is wonderful.
Mr. Moon, who is part American Indian, traveled in a 1975 half-ton Ford van with two worn rear tires and a knock in the water pump. He felt rather worn himself and there was a knock in his heart. He headed for a psychological frontier, a better horizon. He thought that ''just paying attention'' to the world around him might do him good. He was going to try to practice what Whitman called ''the profound lesson of reception.'' Like Whitman, he said, ''O public road, you express me better than I can express myself.''
The job Mr. Moon had lost was teaching English, but in ''Blue Highways'' he goes on teaching, teaching us, as Proudhon put it, ''the fecundity of the unexpected.'' Nietzsche wrote that he always trusted thoughts that came while walking, and Mr. Moon amends this to traveling. People tend to say profound things to travelers in the attempt to persuade them to pause in their flight and listen.
''Imageering's my job,'' a man says to Mr. Moon, in a sardonic tone. ''There's no convergence between what I know and what I do.'' ''At times,'' an elderly man remarks, ''I find I miss my nimbleness.'' When Mr. Moon tries to talk about black-white relations to a man in Selma, Ala., the man says, ''You got a picture in your brain all made up like a bed.'' Camping by a stream one night on the edge of the Arizona desert, the author is startled by a man stepping out of the darkness. He, too, is a traveler, in a small way. Though he's a family man, his wife and two daughters won't travel with him. ''Their lives,'' he says,, ''go as far as they can stretch their hair dryer cords.''
''I could write a book about my life,'' the man continues. ''I'd call it 'Ten Thousand Mistakes.' I've made them all. I can't even remember the first 6,000.'' When he was only 6 or 7, he confides to Mr. Moon, his father gave him a long, close look that frightened him. ''Whatever he saw in me,'' he says, ''made him shudder.''
A black hitchhiker looking for work says, ''Seems things I wait for don't come along, and the ones I want to see pass on by, stop and settle in.'' A ''dwindled man'' in a bar in Bagley, Minn., complains to Mr. Moon about baseball announcers. ''Velocity,'' he says. The announcer refers to a pitcher's velocity and a runner's ''good acceleration,'' but ''this is a baseball game, not a NASA shot.'' In California, a very old man in a large camper says he refused to put in any television computer games to entertain his greatgrandchildren. ''Those kids,'' he says, ''won't have anything unless wires come out of it. If I ran an extension cord down my pantleg and let them plug me in, then they'd believe they had a real greatgranddad.''
Mr. Moon's descriptions are just as good as his reported conversations. Of one of the many waitresses he meets, he says ''her voice was deep and soft like water moving in a cavern.'' Another has ''a grudge of a face.'' To a waitress who asks him, ''Whata you lookin' for?'' he answers, ''Harmony.'' According to him, the quality of the food in a small-town diner can be anticipated by the number of calendars on the walls. The more calendars, the better the food.
In almost every small town, Mr. Moon finds, there is a philosopher-historian who waits for someone to whom he can explain the soul of the place and pick the colors out. These keepers of the flame are often elderly, retired people who feel that the small town provides time and space to think in ways that the city does not. One such woman says to the author, ''A teacher should carry a theme - a refrain to sing ideas from.''
According to the map in ''Blue Highways,'' Mr. Moon's trip took him all around the perimeter of the country, as if he wanted to try to grasp it in his arms. On finishing the book, one can be forgiven a little flush of national pride. The range of voices in this nation of ours seems to go all the way from Samuel Beckett to Robert Frost. On Mr. Moon's evidence, we are not yet condemned, as someone put it, to ''an existential landscape - without absolutes, without prototypes, devoted to change and mobility.'' Rather, we are closer to a passage in T.S. Eliot. In one of his uncharacteristic moments of optimism, he wrote: The end of all our exploring Will be to arrive where we started And know the place for the first time.