Ten guests of varying origin are resident, including a French guitar player, a Tuscan doctor, a Venetian glass artisan, an English refugee, a Neapolitan astrologer posing as an artist, and an enigmatic Jansenist.

Imprimatur is many things: anti-clerical tract, Chaucerian comedy, whodunit, history thesis and Dickensian dose of urban underbelly.

"[4] In France, Le Monde asked, "What should be more admired: the keenness, great narrative talent, and knowledge of philologist Rita Monaldi and musicologist Francesco Sorti, or the masterful style and superior quality of language of a captivating literary creation?"

"[1] Some literary critics have suggested that the book recalls many elements of the traditional detective novel, such as those featuring Sherlock Holmes and Dr Watson; or a murder-mystery by Agatha Christie.

[5] Elsewhere, comparisons with the group of characters inhabiting the inn have been drawn with the model used successfully by authors such as Geoffrey Chaucer and Charles Dickens.

In an appendix to the book are listed and examined a number of new historical sources discovered by the authors in the Vatican Archive and the Public Record Office of Rome – previously unknown to modern historians, and confirming the theory of a secret agreement between William III and Innocent XI.

[9][10] For fear of Louis XIV's dominance, not only Innocent but also Catholic leaders such as the king of Spain and the elector of Bavaria supported William of Orange.

[13][14] When news of William's decisive victory over James at the Battle of the Boyne reached Rome, the papal court, still allied with him against Louis XIV, but by then headed by Pope Alexander VIII, is reported to have ordered the singing of a Te Deum of thanksgiving, while similar celebrations were held in Catholic churches in Madrid, Brussels, and Vienna.

[15][16][17][18] Lord Melfort, a strong supporter of King James, reported that the pope "seemed horribly scandalised" that any cathedral had sung a Te Deum for William's victory; but, as historians observed in 1841, "the plain truth is, that William all along had a strong party among the cardinals ... the great principle of the papal court was to check in Italy the progress of the French, who more than once flattered themselves with the hope of becoming masters of the entire Peninsula.

The Roman Catholic Church had been keen to promote Innocent's cause as an active opponent of the Ottomans in the light of the terrorist attack by Islamic fundamentalists on 9/11.