The text mentions that a Sadguru takes 'service' from devotees through books. Can you elaborate on the two types of service described?

According to the preface, a Sadguru accepts service from devotees through books in two distinct ways. The first way is when the Guru themselves creates a monumental work, with examples like the Shri Dnyaneshwari or Shri Dasbodh being cited. The second, and more relevant to building a community around a specific saint like Sai Baba, is when the Guru has his biographies written by his devotees. This act of writing is a form of service. Subsequently, the writer and the wider congregation of devotees perform service by studying and conducting Parayans of these biographies. This dual form of service, as detailed in chapter 0, involves both the creation and the communal study of sacred texts.