Long before Baronius was appointed Librarian of the Vatican in 1597, he had access to material and sources in its archives that were previously unpublished or unused. He utilised these in the development of his work. Accordingly, Annales Ecclesiastici is considered by most as extremely useful and complete. The eminent historian Lord Acton called it "the greatest history of the Church ever written". On the other hand, the atheist writer Joseph McCabe accused it of being "by no means critical; it is intensely Roman Catholic".