Book – Voce del Morte by Vincetti Marcus Giovanni,[sic]
It is a tome that the Giovanni use to communicate with otherwordly beings. It is kept in the mansion in Los Angeles. The fledgling may choose to recover it for Pisha, who will in turn reward the fledgling with the Key of Alamut.
It is encountered in the quest only Giovanni Stronghold on top of the counter in the first room (embalming room) when entering the secret passage. Most miss this and as a result use "give item_g_pisha_book" in the console command to finish the Occultish Personality quest.