Suggest me a book that explores spirituality (not faith or religion)

I recently heard someone recommend a book by the Dalai Lama, which made me curious about spirituality more broadly. I’m interested in books that explore spiritual themes and personal meaning but are accessible to anyone, not tied to a specific religion or meant only for people within a faith tradition.

My goal is to feed my sense of spirituality and inner growth, not to study or adopt a religion.

Any recommendations?