Vaticano Spa (Vatican Ltd) a book about the murky financial dealings of the Catholic church (The subtitle reads: "from a secret archive – the truth about the church's financial and political scandals") has been a runaway success in Italy. Written by journalist Gianluigi Nuzzi and published by the Milan independent publisher Chiarelettere last year, more than 200,000 copies have been sold.

What's all the more astonishing is that this success has been in spite of being ignored by almost all the Italian media, with the exception of a single television programme on La 7, hosted by Gad Lerner.

Why the conspiracy of silence surrounding an Italian bestseller? Why aren't television, newspapers and magazines celebrating the success of a colleague? After all, Nuzzi has written for the Berlusconi family-owned weekly Panorama and now is a journalist for the daily Libero, considered to be the prime minister's house journal.

The explanation, according to Nuzzi, whom I asked for a comment for this article, lies in the subject matter:

"We thought that Karol Wojtyla (Pope John Paul II), as he had promised, would have sorted out the Vatican finances after the scandal of Cardinal Marcinkus and the IOR (the pope's bank).

"But during the 80s and 90s, the whole system of shady deals and bribes was inherited by Marcinkus's successors and became increasingly dishonest and cynical. The pope knew about it, but did nothing to remove the heads of this power network.

"The book, Vaticano Spa, steps inside the sacred palaces and uncovers secrets thanks to the huge archive bequeathed by monsignor Renato Dardozzi, who was summoned to join the 'perestroika' working on the Holy See's finances. My inquiry, which has the merit of not being anti-clerical, was considered the best selling non-fiction title in Italy for 2009 by the American Nielsen ratings.

"But, owing to some form of self-censorship, the television networks have ignored it, possibly because the church still inspires unconditional obsequiousness and fearful reverence. A lost opportunity because this is the first time that the most reserved documents from the pope's bank have been made available."

Aside from the desire not to offend the church, there are underlying political reasons that explain the reluctance of Berlusconi's private and the state-controlled public television channels to publicise this model of journalistic inquiry.

To summarise. For 20 years, until 2007, the CEI (the permanent Episcopal Conference of Italian Bishops) was ruled by cardinal Camillo Ruini, the vicar-general of the diocese of Rome. In Ruini's view, the church should be a pro-Berlusconi political party and he sought out and created ties both with the Northern League with its pantomime paganism and with the so-called "pious atheists" – ie, some of Berlusconi's most fervent supporters in the press. The most influential among these are Giuliano Ferrara, the founder and editor of Il Foglio (which belongs to Veronica Lario, the soon-to-be-divorced Mrs Berlusconi) and Vittorio Feltri, the editor-in-chief of Il Giornale (which belongs to Berlusconi's brother).

Ruini's successor, Cardinal Tarcisio Bertone, believed his predecessor was too openly favourable towards centre-right extremists. Furthermore, Berlusconi's involvement in endless sex scandals and his unbridled lifestyle had become a source of embarrassment to the church. As a result, Bertone encouraged Avvenire, the CEI's daily paper to distance itself from Berlusconi's hedonism, scandals and pending legal problems.

Alarmed that the church was considering an alliance with a future PDL (Berlusconi's party) but excluding Berlusconi himself, the "pious atheists" – the prime minister's National Guards – rode to the rescue.

Vittorio Feltri wrote a front page editorial in his newspaper demanding (and obtaining) the resignation of the editor of l'Avvenire, Dino Boffo. Boffo was accused of hypocrisy for daring to criticise Berlusconi's lifestyle while he himself had been involved in a case of homosexual harassment. The accusation proved false, but Feltri raised the stakes by insinuating he had been informed of the forged document against Boffo by a Vatican source. The mysterious informer was apparently someone in the entourage of Giovanni Maria Vian, the very powerful editor-in-chief of the Vatican daily paper, l'Osservatore Romano.

Against such a background, Nuzzi's outstanding investigation and its astonishing revelations (such as secret accounts registered to charities for research into leukaemia but used to protect high-profile clients) have become a pawn in the gang war in the Curia which Berlusconi's most fanatical supporters have every interest in exacerbating.

Meanwhile the church's unlawful activities, as revealed by the book, seem neither to bother nor to scandalise many people in Italy, perhaps because since the days of Luther, Italian cynics know that the church is an organ of power and that it has little to do with religious sentiment.

• Translated from Italian by Judy Segor