uring the lifetime of Nicolaus Copernicus (1473-1543), Columbus sailed to the New World, Luther defied the pope and Michelangelo painted the ceiling of the Sistine Chapel. Europe was being roused and roiled by forces of change and the world would never again be the same. Shortly before his death, Copernicus himself contributed to the ferment with the opening manifesto of an eventual scientific revolution. His book's bold thesis, in essence, displaced Earth as the center of the universe and, in effect, challenged the Bible, the church and the almost equally revered Aristotle as the last word in cosmology.

Copernicus was an unlikely apostle of an unsanctioned cosmology. No firebrand, he led a quiet life as an astronomer and cleric in northern Poland, which he referred to as that ''far corner of the Earth.'' But he was seized with the radical idea of heliocentrism: contrary to the belief held for more than a millennium, the sun and the other planets do not orbit a motionless Earth; rather, the sun is the center of the planetary system, which includes Earth. He resisted publication, though, perhaps out of the same aversion to controversy that was to afflict Darwin.

Eventually, Georg Joachim Rheticus, a mathematics professor at Wittenberg, Luther's old university, visited Copernicus, became his protege and persuaded him to go public. Rheticus even arranged for the book's printing in Nuremberg in 1543, with the Latin title ''De Revolutionibus Orbium Coelestium Libri Sex'' or ''Six Books on the Revolutions of the Heavenly Spheres.'' Usually referred to simply as ''On the Revolutions,'' the book occupies a lofty place in the history of modern science.

Then why would a serious author in the 20th century judge it ''the book that nobody read?'' This dismissive remark by Arthur Koestler in his 1959 history of early astronomy, ''The Sleepwalkers,'' later inspired Owen Gingerich to undertake a search for all surviving copies of the original two editions of the Copernicus book. He was looking for notes and comments written by readers in the book's ample margins, evidence that might indicate ''On the Revolutions'' had indeed been widely and closely studied.

For Gingerich, an astrophysicist and historian of science at Harvard, the quest became a 30-year obsession described in ''The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus'' -- a fascinating story of a scholar as sleuth. His enthusiasm for what might be judged a rather fine point of history is infectious. His book deserves to be read not only by historians and bibliophiles, but by anyone with a taste for arcane detective adventures and a curiosity about the motivations of scholarly perseverance.

In 1970, with the approach of the 500th anniversary of Copernicus' birth, Gingerich and another historian of science, Jerry Ravetz, were beginning to suspect that Koestler might have been right. They could think of only nine people who almost certainly had read the original Copernicus book: among them, Rheticus and two or three other German professors; the printer and the proofreader; Tycho Brahe, the 16th-century Danish astronomer; possibly Galileo and definitely Johannes Kepler.

(Here is the place for full disclosure: I have never read the Copernicus book cover to cover, only excerpts pertaining to, as the title page promised, the ''wonderful new and admirable hypothesis.'' At least 95 percent of the text, Gingerich tells us, is ''deadly technical,'' allowing me to rationalize that it was better to suffer guilt over not having read it all than to risk the embarrassment of incomprehension if I had.)

Shortly after compiling the list of nine, Gingerich came across a profusely annotated copy in Edinburgh, the first encouraging sign of expert readership. He then followed leads through the byways of astronomy and book publishing in the 16th century, made side excursions into astrology and bookworms (literal as well as figurative), crossed cold-war borders into the vaults and stacks of libraries from Moscow to Melbourne and hobnobbed with rare book dealers and collectors, including some shady operators. Even F.B.I. and Interpol agents joined the chase; a few stolen copies were recovered.

Never does the author despair, and often a visit to a library sends his spirits soaring, as when he ''turned another page and was stopped cold in my tracks'' at the sight of Tycho Brahe's handwriting. He is not unaware that his obsession might strike some as odd: ''Why do I get excited about something as esoteric as this?'' he asks, and then explains the significance of a new insight into Kepler's research.

Gingerich is not always able to sustain the momentum of his narrative. It is not easy to hold interest in a lengthy explication of the repeated revisions to Ptolemy's system of an Earth-centered universe. One also wishes for more pauses here and there, particularly after encountering more obscure characters, for a clarifying digest of where this takes the story.

But never mind; as in most good adventure stories, the rewards are in the pursuit itself. We learn how knowledge spread ever so slowly in a pivotal age. We catch glimpses of Copernicus, about whom little is known. His influence on Kepler's laws of planetary motions is delineated. Annotations in copies belonging to Kepler and to his teacher lead Gingerich to the discovery that the Copernicus book's opening disclaimer -- insisting the thesis is merely hypothetical -- had not been written or subscribed to by the Polish astronomer. That was ''dynamite,'' Gingerich concludes; ''it undermined the church's position that heliocentrism was . . . not to be confused with physical reality.''

We are also given a touching insight into Galileo's conflicted mind. By his time, the early 17th century, the Vatican's anti-Copernican attitude had hardened, and Galileo's interpretation of the moons of Jupiter was heretical. In his last years under house arrest, Galileo, the ever faithful Catholic, dutifully censored passages in his copy of the book, as instructed by the Vatican, though Galileo the scientist ''took care to cross out the original text only lightly so that he could still read it.''

In all, Gingerich's search located 276 copies of the first Copernicus edition and 325 of the second. By his estimate, more than half the volumes printed in the two editions survive, attesting that even then this was recognized as an important book -- and that Koestler was wrong.