BACK in the mid-1970s, everyone, it seemed, was talking about a book called "Zen and the Art of Motorcycle Maintenance." The first work of an unknown writer, Robert M. Pirsig, it had been turned down by 120 publishers before being published at last in 1974, when it was greeted by a chorus of critical acclaim and resounding bestsellerdom.The New York Times pronounced it "profoundly important.Sparkles like an electric dream," said the Village Voice in the parlance of the moment. Writing in The New Yorker, George Steiner went even further: "the narrative tact, the perfect economy of effect defy criticism," proclaimed this well-known critic. "The analogies with 'Moby Dick' are patent," he declared. "Robert Pirsig invites the prodigious comparison.... What more can one say?" What more indeed! It makes one wonder what sort of reception Pirsig's second book, "Lila," will be accorded now, 17 years later. Will it be a second succes fou with a new generation of readers, or will those who were so swept off their feet by the first book have decided in the interim that they went a little too far and use the second work as an opportunity to revise their opinion downward? Having now had the chance to read both books side by side, I detect no diminution in quality. "Lila" is not a belated after-thought or a pale repetition of "Zen," but a worthy continuation of the author's quest. In some respects, it is a more interesting work. But neither invites comparison with "Moby Dick." And neither, I think, is a literary masterpiece. Both are the work of a man who has done a lot of thinking and has something to say. Subtitled "An Inquiry into Morals" (just as "Zen" was subtitled "An Inquiry into Values"), "Lila," like its predecessor, is a narrative so full of ruminations that it sometimes seems little more than a clothesline from which Pirsig hangs his collection of essays on a wide but interrelated range of topics from metaphysics to motorcycles. The narrator/philosopher/hero of both books is called Phaedrus. In the first book, he spent a lot of time explaining the practical and symbolic importance of learning how to keep one's motorcycle in good working order. In "Lila," we find him cruising America's waterways in an ocean-worthy sailboat with an auxiliary motor. As the story opens, he is in upstate New York, headed for New York City and the open sea. In a riverfront bar, he allows himself to be picked up by Lila. She's the kind of woman who's been around, a curious mixture of toughness and vulnerability, bluntness and complication. Phaedrus has also made the acquaintance of a man named Richard Rigel, who warns him that Lila is "evil." Rigel disapproves of Phaedrus's decision to let Lila join him on his voyage. In fact, Rigel even disapproves of Phaedrus's earlier book: You talked for chapter after chapter about how to preserve the underlying form of a motorcycle, he tells Phaedrus, but you didn't say a single word about how to preserve the underlying form of society. Rigel further accuses Phaedrus of being too isolated to understand the values of the community around him. In the chapters that follow, Phaedrus - and Pirsig - try to answer this criticism by working out a philosophy that takes account of two kinds of values: static and dynamic. Although dynamic values (those that are still in the process of being discovered) are often at odds with static values (those that are already held and believed in), both kinds are necessary, as he defines them for us: "Each culture has its own pattern of static good derived from fixed laws and the traditions and values that underlie them. This pattern of static good is the essential structure of the culture.... "But in addition there's a Dynamic good that is outside of any culture, that cannot be contained by any system of precepts, but has to be continually rediscovered as a culture evolves. Good and evil are not entirely a matter of tribal custom. If they were, no ... change would be possible...." Phaedrus/Pirsig admits that in the past he had tended to undervalue the importance of static patterns in his enthusiasm for the dynamic. But now he sees that "Dynamic Quality alone ... has no staying power," and that the static patterns provide a "stabilizing force" that protects dynamic progress from degenerating into chaos. Looking back on the 1960s - and back through history - he admits it can be hard to tell the forces of progressive change from the forces of degeneration that threaten to tear societ y apart. Phaedrus's fascinating speculations and theorizings, his ambitious plan to come up with a metaphysics that will show how philosophical, scientific, aesthetic, and moral truths are interrelated - all this is challenged and threatened by the presence of Lila on his boat. Confronting her erratic behavior, Phaedrus is continually reminded of how difficult it can be to deal with the unexpected and the unknown. As in his earlier book, storyline and essay are interwoven: In the case of "Lila," the storyline contains more elements and characters that are purely fictional. Readers in search of a good old-fashioned adventure yarn about voyaging down the Hudson will doubtless be surprised to encounter chapter after chapter devoted to disquisitions on everything from East Indian religions to American Indian culture. And, along with scores of intriguing observations on these and other phenomena, there is also an ambitious attempt to synthesize these insights in a system that places values rather than facts or things at the very center of reality. "Lila" is the kind of book that asks questions like "Why ... should a group of simple, stable compounds of carbon, hydrogen, oxygen and nitrogen struggle for billions of years to organize themselves into a professor of chemistry?" It is cranky, original (perhaps a little less wholly original than its autodidactic author might suppose), occasionally repetitious, but almost always thought-provoking. While neither this book nor its predecessor would seem to merit the kind of extravagant praise reviewers dished out in 1974, what both books prove is that when a writer sets out to tackle issues that really matter to him, the writer's deep interest in what he writes can have the power to compel readers' interest, too.