The celebrity ghost-written memoir is the non-fiction form de nos jours. Publishers see it as a winner that combines quality narrative with mass-market appeal. Such memoirs do not even need to contain fresh insight when there is an established fanbase. Just ask Prince Harry about the trouble it causes when a revelation does shock. The idea that a pope should put his name to a co-developed text is nevertheless novel. Of Pope Francis’s predecessors, only that preening Renaissance man of letters Pius II Piccolomini contributed to the genre directly. Piccolomini’s Commentaries, though light-hearted Latin, are also a self-indulgent, self-justifying piece of self-invention. The precedent for Francis does not encourage.