In addition to librarian position, Cancellieri was also Superintendent of the Propaganda printing press, and for a time, Prosigillatore for the Vatican, (Deputy Sealer of Briefs).
He was amiable and neat in person and language, but never terse; and his style in manners and writing were bountifully steeped with gushingly effusive, but also often grating, cordialities.
Trollope states: The old 18th century bookworm, whose mind, filled to overflowing with odds and ends of archaeological learning ...could never conceive, that his stores could be otherwise than profoundly interesting to all mankind, must necessarily have seemed an unprofitable cumberer of the earth to the young poet, whose brain was busy with meditations on the eternal destinies of man.
The gentle old-world courtesies in 'issimo,' ... nauseated the younger man, whose provincial breeding had not taught him to understand that there was no more real insincerity in his aged host's compliments than in the obeisances of a minuet.
But it may be affirmed, with the most perfect assurance, that Cancellieri's intention and object at the interview was to please and gratify his visitor, whereas the morbid, melancholy, discontented mind of the poet was wholly occupied by his own sensations.His books reflect his style; and, speak generally on the traditions of papal Rome, but also he took time to comment on Tarantism and claims surrounding the origins and actions of Christopher Columbus, about the Catholic liturgy, the sacred and ancient topography of Rome and its surroundings.
His essays begin with short islands of statements, but rapidly these are surrounded by an ocean of footnotes, an erudite diluvium of quotations and citations, resembling the style of the modern novel The Mezzanine by Nicholson Baker.
Cancillieri was educated and focused on the courtly atmosphere and world of the Roman Curia, replete with genuflection, cult, and ritual; and all this was nearly dissipated by the uncompromising grapeshot of post-Revolutionary Napoleonic France.