That same year he received an M.A. and his Ph.D. in Philosophical Theology in 1990 at the University of Tubingen in Germany. O'Donohue returned to Ireland in 1990 where he continued his priestly duties and began post-doctoral work on Meister Eckhart. With the publication of Anam Cara in 1997, he became international bestselling author. Next was Eternal Echoes in 1998. In 2000, O'Donohue published  Conamara Blues, a collection of his poems. O'Donohue left the formal priesthood  at the end of that year and focused on his writing and social justice. Beauty:The Invisible Embrace was published in 2003.  Just two months before his unexpected death in January 2008, his final book, To Bless The Space Between Us, was published in Ireland. O'Donohue's influence on Celtic writing and spirituality continues to be strongly felt by those devoted to his writing and by new admirers.  His family holds his unpublished works in their care with the intention of eventual publication.