I don't believe the scriptures supports salvation outside of the church; you are either a part of God's church or you're not. Given the author's conclusion, there is no salvation outside of the church. So can you be saved and not be a member of the Catholic Church, or not? Is that what our Catholic friends would like to say?
I would offer another point of view:
Christian, I Presume? (Salvation) [Ecumenical]
Rock Solid: The Salvation History of the Catholic Church [Ecumenical]
Getting in Touch With Reality (good character and behavior as a ticket to Heaven)
The Early Church Fathers on Salvation Outside the Church [Catholic/Orthodox Caucus]
Extra ecclesiam - Outside the Church there is no salvation.
Is Faith Necessary for Salvation? (Part 2)
Good Will Equals Salvation? (Did the pope say non christians could be saved - part 1)
The Experience of the Salvation of Christ Today