Mistborn. Wouldn't say it changed my life but it really put into words how I feel about religion so I could better communicate it to others. Don't want to spoil anything for anyone but I personally thought the story wrapped up well.

Professionally it was Radical Candor by Kim Scott. I was a struggling new manager from an individual contributor role and it really helped me develop a mindset and ability to set expectations but at the same time assist with their growth.