Can you explain the two types of service a Sadguru takes from devotees through books and how this relates to building a community?

Chapter 0 outlines two ways a Sadguru accepts service from devotees through literary works, both of which are instrumental in building a spiritual community. The first is when the Guru themselves creates a great work. The second, more relevant to Sai Baba's community, is when the Guru has their biography written by devotees. This biography, such as the Shri Sai Satcharita, is then accepted for service in the form of study and Parayans by both the writer and the broader congregation of devotees. This shared act of engaging with the Guru's life story becomes a communal spiritual practice, uniting followers and allowing them to collectively serve the Guru.