PRIVATE RENAISSANCE: <i> by Maria Bellonci; translated by William Weaver (William Morrow: $22.95; 464 pp.) </i>

Italy’s noted woman of letters, cultural historian Maria Bellonci, was no stranger to the feudal courts of the Italian Renaissance. Before her death in 1986 at 83, she had spent a career wending through the well-documented events and intrigues that fueled Europe during that heady time and produced five fine histories, including the biographies, “The Prince of Mantua” and “Lucrezia Borgia.” For her final work, however, she chose to write her first historical novel, based on the life of one of the period’s most dynamic personalities: Isabella D’Este, the brilliant marchesana of Mantua.

It’s tempting to say that only the most ham-handed writer could fail to produce a compelling narrative when dealing with as rich a subject as “la madama illustrissima. “ Isabella D’Este defines the term Renaissance Woman as we use it today. Born into one of the oldest families of Italy, the ruling house of Ferrara, Isabella from the earliest days showed an intelligence and maturity far beyond her age. She was fluent in classics, knew science, was a skilled musician and composer, and had a fine eye and voracious appetite for art and a personal sense of style that set the fashion standards of her day. After her marriage at 16 to Francesco Gonzaga, marchese of neighboring Mantua, their court became one of the smartest and liveliest in Italy.

It was as political manipulator, however, that Isabella showed a dexterity outstripping even her husband and eldest son and heir, Federico. For a northern territory such as Mantua, modest in size but strategically placed, life was a continuous diplomatic tap dance. French kings, Spanish emperors, avaricious popes and eager neighbors were constantly prowling for new land, either through conquest or marriage. Though her chances to reign were few--while Francesco was held captive by the Venetians, and after his death, as Federico’s regent--she was always ready and eager. Using a combination of cold-blooded pragmatism, feminine charm and the well-timed but subtle bribe, Isabella managed to keep the many dogs at bay, even in the most dire of crises.

These virtues are admired by Bellonci, even as she has the immodest marchesana admire them in herself. In that “Private Renaissance” becomes a very personal work--you understand immediately why this skilled historian was so attracted to this fascinating figure, why she abandoned straight history for her alone. While the book is every bit as scholarly as Bellonci’s other works--Isabella left behind nearly 2,000 letters, which form the backbone of Bellonci’s portrait--fiction has allowed her the freedom to play. To be, in essence, Isabella. The result is a narrative of great energy and power.

The novel takes shape as a single evening’s reminiscences by the aging Isabella in the year 1533, soon after the birth of Federico’s heir and six years before her own death at 65. Sitting in her room of one hundred clocks, Isabella reflects on the past even as she contemplates the future. Her flashbacks are roughly chronological (some of the breaks in time can throw you), and they are punctuated by letters from the English priest Robert de la Pole, an adoring, lifelong correspondent of Isabella’s whom she never once answers. The fictional De la Pole is Bellonci’s one overindulgence--while the information he brings helps drive the story, his obsequiousness often makes him merely annoying.

But finding faults is difficult. The book is dense--like attacking a large chef’s salad, where you chew and chew but the level never seems to dip--but from events, not language. It is always gripping. There is a real mastery in the way Bellonci makes us see the marchesana’s flaws as well as her strengths, even though the egotistical Isabella (a historical fact) is controlling our view of events. You instinctively trust that Bellonci never takes liberties with the facts, and you end up feeling you’ve read more history than fiction.

No review would be complete without a mention of the supreme grace and style of William Weaver’s translation, which brings the spirit of both Isabella and her biographer to American eyes. One complaint: The publishers opted to omit a cast of characters and scene-setting introduction, and readers must struggle alone through the tangle of Gonzagas, D’Estes and Borgias and ever-changing alliances. It does all come together finally, but not without some initial bewilderment. (Would Italian readers feel comfortable plunked into the middle of the Civil War?) A dose of Renaissance history, or a standard biography of Isabella D’Este such as George Marek’s, makes the reading of this compelling novel all the more pleasurable.