In nine books dealing with such disasters as earthquakes, plane crashes, shipwrecks and epidemics ("Voyage of the Damned," "Enola Gay," "The Day the Bubble Burst," "The Day Guernica Died") Gordon Thomas and Max Morgan-Witts have established a substantial reputation for reporting that is as solid as it is vivid. Their efforts have enjoyed a Hollywood success that is rare for nonfiction--undoubtedly because they clothe their facts in the kind of small, concrete detail that is one of the virtues of good fiction; because they take the reader into the minds and feelings of the real people they write about as though these characters were their own creations.

With "Pontiff," they venture into a new kind of subject and a special set of journalistic challenges. Their topic is the attempt to assassinate Pope John Paul II on May 13, 1981, in St. Peter's Square and the events leading up to that tumultuous moment.

The book moves toward its climax from two directions, tracing the historic events that brought a Polish clergyman, Karol Wojtyla, and a fanatical young Turkish terrorist, Mehmet Ali Agca, to their brief, violent encounter in a vast, open square crowded with cheering pilgrims.

Before they portray the shots ringing out and the blood spreading across the pope's white robes, their book intrudes into all kinds of secret places: the archives of several intelligence agencies, a terrorist training camp in Libya, the back rooms of the Vatican Secretariat of State and the Sistine Chapel during a conclave of cardinals summoned to elect a new pope. Startling revelations and unsuspected facts behind the headlines are their stock in trade throughout "Pontiff."

This book also takes them into the new territory of Vaticanology, an uncharted Sargasso Sea for investigative journalists, where facts are often unobtainable and quotations unattributable.

Vatican City is a land of ambiguous whispers in dark, private places. Publicly, it is the home of "cardinalspeak," an elaborate language in which an apparently simple statement--the theme of a sermon, for example--can conceal layers upon layers of hidden meaning. It is the headquarters for an enormous worldwide church and for a government that has virtually no territory but highly significant economic resources and considerable diplomatic status.

As church and as state, the Vatican cultivates an atmosphere of almost paranoid secrecy. For nearly two millenniums it has been developing subtleties and complexities in its thinking, its goals and its procedures that can easily trap the uninitiated observer into simplifications that amount to distortions.

The authors entered this journalistic never-never land with full awareness of where they were going and what they were doing. They show that awareness deftly in their discussion of the work of other Vaticanologists--this observation, for example, on how the world press prepared for the conclave that elected Pope John Paul II: "They blissfully continue to interpret the uninterpretable, judge the unjudgeable, put flesh and blood on the Holy Spirit and perhaps even give it shoes to see where the Spirit goes in order to postulate why . . . Like all other ologists, the Vaticanologists are really no more than outsiders peering in, attempting to penetrate the unpenetrable sic ."

The Vatican is not actually the most impenetrable bastion the authors attempt to storm; they also venture into Kremlinology, with considerably less concrete detail than they muster for the Vatican but with an appalling (though not wholly unexpected) conclusion: the attempt on the pope's life was probably engineered by the KGB in retaliation for the secret encouragement and support he had given Lech Walesa before Solidarity made its first major demonstrations in Poland. If their Kremlinology is as scrupulous as their Vaticanology, the charge deserves serious consideration.

Their documentation on Vatican sources is not ideal--in the circumstances it could not be--but it is better than what we usually get from that part of the world.

Whatever their credibility (and usually it seems high), there is no question at all about their readability. They carefully avoid inventing quotes, but they are lavish with plausible details--a nun peeking through a keyhole into the papal bedroom where John Paul I lies dead but undiscovered; a group of Vatican politician-scholars in a secret room searching through centuries-old manuscripts to find a precedent for a papal autopsy; the fumes of tobacco smoke swirling in a secret conclave of cardinals; the shattering of a coffee cup (with "a little" cream and sugar) on the pope's desk as Russian Metropolitan Nikodim (the archbishop of Leningrad) dies of a heart attack during a papal audience.

They handle highly dramatic material, and they handle it with clarity and impact: not only the assassination attempt itself, but the tangled situation of the Vatican in recent years, the stagnation toward the end of the reign of Pope Paul VI, the colorful 33-day reign of John Paul I, the complex and sometimes rather dubious financial dealings of the Vatican, the turbulence of a very old church trying to find its way through the 1980s with many members in revolt, the bitterness of Third World terrorists and the callous manipulation they suffer from their communist allies.

The authors' literary style is sometimes flawed and their sources are sometimes vague, but they have assembled an enormous mass of complex material in a readable, credible form.