Jesuit Father Federico Lombardi, spokesman for the Vatican, said soon after the Pope arrived at his summer residence of Castel Gandolfo, near Rome, on July 7 he appeared fully "restored and beaming".
He said the Pope "immediately began to dedicate himself to reading and studying ... It's clear, therefore, how important it is for him to finish this great project begun years ago".
The pontiff began writing the first volume of the work in the summer of 2003, two years before he was elected Pope.
Pictures released of the Pope on holiday at Castel Gandolfo, in the hills overlooking Rome, show him feeding the fish, reading Vatican newspaper L'Osservatore Romano and taking walks in the garden.
SIC: TDTUK