The book is called "Big Sky Mind: Buddhism and the Beat Generation" (Carole Tonkinson). Consider finding or getting: https://www.amazon.com/Big-Sky-Mind-Buddhism-Generation/dp/1573225010. It contains essays, poems, photographs, and letters between different authors: seems very interesting and useful!
How does this relate to my thesis? Spirituality would need to be an essential part of my thesis, since I wish to consider how the lifestyle of authors of the Beat Generation blurs the defines between what is usually considered "life" and what is usually considered "literature". If I aim to show that they were "practical artists", or "performative artists" in some way (need theoretical background here), their spirituality would be an essential part of this definition, as it was an essential part of their life.
See how in the essay "Prose Contribution to the Cuban Revolution" he says "That's the karma I wanted, to be a saint" (The Essential Ginsberg). Being a saint comes before being a writer.