Slow going. In late summer and early fall, 1980, freelancer Shapiro trekked from Dillon Beach, Calif., to Central Park, covering 3,026 miles in 80 days (10 of which he spent nursing various injuries). It was far from record time (one Frank Giannino left California a month later and still beat Shapiro to New York by a day), but records were the last thing on Shapiro's mind. His transcontinental run was a Zen exercise, a vision quest, a search for the real America, an attempt to exorcise personal demons--not to mention the book contract he'd already signed. And that's the problem with Shapiro's otherwise intelligent and well-written diary: he's trying too hard to have and record A Meaningful Experience. He's so self-conscious, so wrapped up in the trials and failures of his anti-heroic existence that he can't relax and entertain us. The possibilities are right there: what vantage point could be more absurd than a skinny pedestrian's, loping down I-80? Instead, Shapiro takes everything to heart. When momentarily fooled into returning a brotherly hand-wave to a plastic cut-out hand jiggling on a truck driver's windshield, Shapiro notes: ""It was a cosmic greeting this quickie item extended. But to give up your own personal commitment to the expression of friendliness, to surrender the effort needed to raise your hand in salutation to a spring and piece of plastic--."" Such ponderosities aside, Shapiro evokes the physical sensations of the run well enough--the burning sun, the mashed animals by the roadside, Western rednecks, just-folksy Nebraska and Iowa, etc. But over the long haul, his nervous, humorless sincerity drags like a fiat-footed marathoner.