What are some books that hit you on a profoundly spiritual level at a critical moment in your life?

As a male freshly entering his 40s, I'm finding myself of what I guess you could say is a crisis of meaning; I suppose its probably a pretty classic case that countless before me have gone through. So I'm asking for book recommendations that maybe helped you out in a similar phase of life. Books that might not be explicitly "spiritual books" per se – and maybe its even better if they aren't actually – but these could be fiction or non-fiction, sci-fi tales or memoirs, anything really. As long as it evoked a deep stirring within you and helped you on your own life journey in a profound way.

For context, I was born into a Christian family and counted myself as a true believer until my 20s when my worldview began to shift and I started exploring other facets of my self and my sense of spirituality. I've meandered casually through buddhism and atheism, but now kind of just consider myself a humanist, which I hold loosely. I'm hoping to find some books that are deeply relatable, that can help me reignite a sense of meaning and inspire me. Thanks in advance for your recommendations!