Excellent post.
No book list is complete without a reading of Ratzinger’s “On the Way To Jesus Christ” and “The Apostles.”
But clearly, Ratzinger’s most definite thesis on why salvific hope lies only through the Catholic Church is in his tour-de-force publication “Iesus Dominus”
All Catholics need to give this a careful read.
Fortunately it's not our call as to who will recognize that Truth and accept it. As Lewis himself said about the Final Judgment - "there will be surprises."