If I’m understanding correctly, the person isn’t convinced that Buddhism isn’t as good as Christianity and seems not to believe in God? Anyway . . . .
Two excellent books by non-Catholics:
Simply Christian - N.T. Wright
The Reason for God: Belief in an Age of Skepticism - Timothy Keller
Finding True Happiness - Fr. Robert Spitzer
Catholicism: A Journey to the Heart of the Faith - Bishop Robert Barron
The Lord - Romano Guardini
Joseph Ratzinger (Pope Benedict)'s Introduction to Christianity and Jesus of Nazareth books
The writings of C.S. Lewis and Peter Kreeft!