Accordingly, last year, a certain book of the Saracens, of great authority to them, came to our hands. A certain astrologer of theirs, who the Saracens consider to be a great prophet, had written it from the beginning of their law with the greatest devotion.

As Brewer observes in a footnote, the work is now lost, "but several similar texts in Latin and Old French have been preserved." These, he notes, are edited in Reinhold Röhricht.

This book, included in what would later be called "The Revelations of the blessed Peter the apostle by his disciple Clement, brought together in one volume" helped link the deeds of the Fifth Crusade to ancient prophecy and used Prester John as the point of connection. Attributed to Pope Clement I (35-99), the text 

Oliver of Paderborn identifies the aforementioned text as the Book of Clement in his History of Damietta (qtd. in Brewer, p. 138):

Certainly, after the capture of Damietta, the legate to the apostolic seat [i.e. Pelagius] ordered the book written in Arabic to be briefly read aloud by an interpreter to the ears of the multitude; examining and observing its bindings along with the pages, we found it to be beyond ancient. It is entitled "The Book of Clement," written so they say from tbe mouth of the prince of the apostles by Clement himself about the revelations made to Peter between the resurrectionand the ascension by the Lord. This book begins with the creation of  the world and concludes with the end of time; the teachings and precepts for salv tion are read in it. It also mentions prophecies, some of which have evidently n w been completed, and some of which hang in the future. Amongst other things, it is said that a city abounding in water would be captured by the Christians along with one city of Egypt. It mentions the capture of Alexandria, nor is Damascus left unmentioned, which greatly tormented and [still] torments God's servants. It thereafter discusses two kings who will come to Jerusalem, one of which it is said will come from the East, the other from the West, and which will take in the year in which Easter will fall on the third day of April.