According to Luke

This is an odd one, not least because it claims to be a novel, which it isn’t. Emmanuel Carrère, writer and film-maker, looks back on an earlier self when, as a young man, he had a phase of being a devout Catholic, going to Mass daily, making his confession, the whole caboodle. He decides to marry his girlfriend, who is called Anne. We do not hear much about her. He later marries Hélène Devynck. Like the ‘real’ Carrère, the narrator has a house on the island of Patmos, where much of this book was written — appropriately, since it is a (sort of) commentary on the New Testament.

As Carrère modestly says, everyone who has ever investigated the origins of Christianity ends up surveying the same relatively small number of sources and documents: the New Testament itself, obviously; the writings of Flavius Josephus, the historian who recorded the Roman destruction of Jerusalem in AD 70; the Dead Sea Scrolls (not much there to help us).