The spokesman said the publication of the letters violates the right to privacy and the "freedom of correspondence" of Pope Benedict, the letter writers and some of the pope's closest collaborators.

In the letters, which include accusations of corruption and financial mismanagement in the Vatican, and focus heavily on internal Italian church matters or Vatican-Italian relations, Cardinal Tarcisio Bertone, Vatican secretary of state, is particularly presented in an unfavorable light.

In late April, Pope Benedict appointed three retired cardinals to a commission to investigate the leaking of the letters.

Father Lombardi said, "The Holy See will continue to explore the different implications of these acts of violation of the privacy and dignity of the Holy Father -- as a person and as the supreme authority of the church and Vatican City State -- and will take appropriate steps so that the authors of the theft, those who received stolen property and those who disclosed confidential information, using illegally obtained private documents for commercial use, answer for their acts before the law."

Nuzzi's book was published May 17 and immediately went to the No. 1 spot on the Italian best-selling books lists.

Facsimiles of dozens of letters and notes are printed in the back of the book. But more than 100 others are quoted -- in part or entirely -- within the book's chapters focusing on "corruption" in the Vatican, making donations in exchange for a personal meeting with the pope, Vatican-Italian relations, the thirst for power among curia officials, the influence of new religious orders and movements and the way church officials handle a variety of scandals around the globe.

The reproductions include a note from an Italian television host to the pope's personal secretary and a copy of a check for 10,000 euro (about $12,650) with a handwritten postscript saying, "When can we have a meeting to greet the Holy Father?"

The book includes what Nuzzi says is the Vatican's decryption of a message from the Vatican nunciature in Washington passing on a request from Chicago Cardinal Francis E. George that the Secretariat of State intervene to prevent the Rome-based Community of Sant'Egidio from giving an award to Illinois Gov. Pat Quinn. Sant'Egidio, a lay movement involved in a variety of social issues, apparently planned to honor Quinn for abolishing the death penalty in Illinois.

The nunciature said that while Quinn is Catholic, the cardinal felt the honor was "inopportune" because of the governor's support for gay marriage and legalized abortion and because Illinois refused to renew foster care and adoption contracts with Catholic Charities in four dioceses.