What are the primary ways a Sadguru accepts service from devotees through literature, and how does this foster a community?

According to the preface in Chapter 0, a Sadguru accepts service from devotees through books in two main ways. The first is when the Guru creates great works themselves, like the Shri Dnyaneshwari. The second, more common method, is when the Guru has their biographies written by devotees. The community of devotees then accepts this service in the form of study and performing Parayans (devotional readings). This shared practice of studying a detailed biography, such as the Shri Sai Satcharita, helps devotees achieve the purpose of their lives and builds a strong spiritual community around the Guru's teachings.