I was once an atheist, so I feel like I know where your friend is coming from. I had a desire to know truth and pursued it even if it hurt me. And boy, did it hurt me.
The 2 books that pulled me off the atheism path were
“Late Great Planet Earth” by Hal Lindsey. Largest selling nonfiction title of the entire decade of the 1970’s. It’s a bit dated now. It’s about bible prophecies coming true in these end times.
“Jesus: God, Ghost or Guru” by Buell and Hyder. It is about the historical evidence that Jesus claimed to be God Himself. A similar book for this timeframe is “The case for Christ” by Lee Stroebel.
The atheists I encounter are not honest with themselves. They refuse to acknowledge the historical evidence that Jesus claimed equality with God (and paid for that statement with His own life) because their bigotry forces them to view christians as irrational followers of a superstition. If they honestly value truth, they would encounter the evidence. I will pray for your friend.
Thank you for your prayers, dear Kevmo, and for sharing your testimony!