The source mentions two types of service a Sadguru takes through books. Can you elaborate on these and explain how they relate to a devotee's spiritual growth?

As outlined in Chapter 0, a Sadguru accepts service through books in two primary ways. The first is when the Guru themselves creates a monumental work, such as the Shri Dnyaneshwari. The second, more relevant to Sai Baba's devotees, is when the Guru has his biography written through a devotee. In this case, both the writer and the readers perform a service. The writer serves by creating the work, and the congregation of devotees serves by studying it and performing Parayans. This engagement is shown to help devotees achieve their life's purpose, suggesting it is a powerful method for fostering spiritual growth and overcoming periods of stagnation.