Sounds like the perfect beach book for me. I ordered it and will read it this winter on vacation.
Without previewing the book, it sounds much like a western version of eastern Zen/Tao philosophy. Let go, less is more, be at harmony and peace with your surroundings. There are terms for that without the word "spiritual." It is called "inner peace" and "serenity." One can be "enlightened" when they realize what it takes to get this feeling.
You don't have to be religious to benefit from eastern philosophy. But I tend to agree with others that your "spirituality" is not an achieved "oneness" with the universe, but rather a journey down a path that your own mind wants to go, so different for each person and their focuses.
I like to say that "spiritual" is everything that is not secular. "Secular" is labor and paying for things. But "spiritual" is enjoying life and other people, and includes escaping from daily routines in any way. It can include work and paying the bills when you reflect on what those things do for your character.