Radio Replies From The Golden Age of Catholic Apologetics

Two priests in the early part of the 20th century had a heart for evangelization and apologetics. One priest, Father Rumble was a convert to the faith from Protestantism and had a radio program  in Australia where he would answer questions about the Catholic faith. Unbeknownst to him, Father Carty, a Catholic priest in Minnesota, was doing street preaching and handing out tracts and literature including a printed version of Father Rumble's radio program questions.
Father Carty contacted Father Rumble and they collaborated and produced an American version of Radio Replies and it went on to become so successful they published 3 volumes. Though the two priests never actually met in real life, their apologetic work continues to be available in book form as well as online for free.
  Check out this link to Radio Replies.  You will find very solid answers to many of the common questions about the faith.