The Cure D'Ars
This is a fascinating and surprisingly readable (but lengthy) biography of St. John Vianney - the definitive one, carefully researched from the documents produced for the canonization process. It is most suitable for adults, but will be appropriate for teens who enjoy reading - it is particularly beneficial for young men considering the priesthood. Some of the particular stories about St. John Vianney and those whose lives he touched are absolutely amazing.