I love Lamott's style. She writes like she's talking to you, and not in a forced or condescending way. She's so open about her emotions and struggles that it's impossible not to relate to her. That same openness also contributes to a feeling of humility as your read her work. Another benefit to this one is that each essay is short enough to read in less than half an hour, making for a great devotional moment during your day, if you like such things.
Again, the book flows so well and is so accessible, I think it will appeal to a wide variety of people, and not just a wide variety of readers. It'll also appeal to people at various places of spirituality and belief. It's not just written for evangelical Christians, it's something that applies to anyone with a belief in God, or, as Lamott says, a "higher power."
I was thrilled to have picked it up from the library on a whim and I'll definitely purchase a copy for my collection at some point.