While it is somewhat well known that Cardinal Ratzinger, before he became Pope Benedict XVI, did not see himself as being on the track to become pope, it may be lesser known that he personally requested to retire as Vatican librarian :
When Cardinal Joseph Ratzinger turned 70 in 1997, he asked Pope John Paul to relieve him of his duties as prefect of the Congregation for the Doctrine of the Faith and permit him to become archivist of the Vatican Secret Archives and librarian of the Vatican Library . . . .
Yes, we always knew he loved to read and write books. Benedict XVI later spoke on the subject: In his providential design the Lord had other plans for me and here I am with you today, not as a passionate scholar of ancient texts . . . .”
Incidentally, the Vatican Library, which reopens next month after having been closed for three years for renovation, does not check out books to the public. As the Catholic News Service reports, “The only person allowed to check out a book is the pope.”