BOOK REVIEW : Another Voice Tries Deciphering Dylan’s : HARD RAIN: A Dylan Commentary <i> by Tim Riley</i> ; Knopf; $23,400 pages

Is Bob Dylan “the most important American rock ‘n’ roller since Elvis Presley?”

So says Tim Riley in “Hard Rain,” a book that allows us to understand exactly why Bob Dylan is so celebrated: The man and his music have provided the raw material for a whole generation of misplaced academics like Riley. While gifted at exegesis, these misfits prefer the pages of “Rolling Stone” to, say, the proceedings of the Modern Language Assn.

Album by album, song by song, sometimes verse by verse, Riley ponders the lyrics, arrangements and delivery of Dylan’s work, from his first album in 1962 to the most recent outing of the Traveling Wilburys.

Riley has adopted (and mastered) the approved idiom of high-toned rock criticism invented by Greil Marcus, an approach that applies hermeneutics, cultural anthropology, textual deconstructionism and social history to the down-and-dirty artifacts of rock ‘n’ roll. And so, with “Hard Rain,” Riley writes his own ticket into the canon of Dylan tribute literature.

Still, it’s also true that Riley sometimes writes himself out on a limb. We wonder, for example, exactly what the hell he’s talking about when he observes that Dylan’s “songs and deliveries are as point-blank as a chess match: reckless sacrifices, offenses posing as defenses, cunning cloaked in ritual, and intellectual muscle draped in flirtatious gamesmanship.”

Now and then, Riley seems to admit that there’s a hustle going on here. He even uses the word con to describe how Dylan uses a “coyote yowl” and “titanic illogic” to convince his more devoted audiences “not just that fate turns on his singing, but that his rash fits of imagery make internal sense.”

Riley recognizes that Dylan is “a media magician who fashions his own mass-outsider cult,” and he cops to the fact that Dylan knows exactly what’s he doing when he strikes the pose of the “poet-jester,” “the counterculture’s anointed bard,” and “the 60s’ singing soothsayer”--it’s all part of what Riley calls “Dylan’s media hustle.”

“Dylan made his persona a subject of his songs from the start,” Riley points out. “As rock’s Zelig, Dylan’s pop persona became his obsession.”

After following Riley into the thicket of Dylan’s life, work and myth, I began to wonder if there isn’t less here than meets the ear. Riley himself pokes fun at the “rapt absurdism” of overzealous critics, but he still finds it within himself to write of Dylan’s “I Want You”: “This song courts critical perplex.”

Then, again, maybe Riley is actually making a feint at irony. After all, he makes a rather stinging point about America’s “pop icon” when he compares Dylan to none other than the Material Girl:

“You can even interpret the career of Madonna,” he writes, “as homage to the Dylan school of how to exploit the press, control your material, train your players to read vocal cues, and navigate a hyper-conscious series of reversals to the point where your image not only sells albums but enhances them.”

Riley is disposed toward superlatives--Dylan is “rock’s most self-conscious performer” and “rock’s least likely long-running act”--but his enthusiasm begins to flag after Dylan’s 1976 album, “Hard Rain.” And Riley’s book ends in exasperation, disappointment, and glum resignation.

“Beginning with Street Legal (1978),” Riley concludes, “Dylan’s voice began to falter, his songwriting waned, and he never wrote to his potential as much as kept his listeners lying in wait for a sudden resurgence of the vitality he once commanded.”

Dylan endures, Riley insists, because he is no longer merely a singer or a songwriter or even a “poet”--he is “an American pop icon.”

“Dylan’s voice,” Riley rhapsodizes, “registers the duplicities rooted in the 60s mind-set he helped to shape: arrogance and insecurity; acute class consciousness and free-spirited utopianism; general resentment and communal solidarity; personal odysseys that were traced inside political vistas.”

But Dylan endures, too, precisely because he is so closely studied and so ardently celebrated by the chorus of critics that now includes Tim Riley.

Toward the end of “Hard Rain,” when Riley pauses to reflect on Van Morrison and compare him favorably to Bob Dylan--”Morrison can find repose in fleet tempos,” writes Riley, “and turn genre moves into extraordinary orbits of emotion”--I found myself wondering exactly why Dylan has so many hagiographers and Morrison has none at all.