According to the provided text, what are the different ways a Sadguru accepts service from devotees through the medium of books?

Chapter 0 describes two primary ways a Sadguru takes service from devotees through books. The first method is when the Sadguru creates profound spiritual works themselves, with examples cited such as Shri Dnyaneshwari or Shri Dasbodh. The second method involves the Sadguru having their biographies written by their devotees. In this case, the Guru accepts service in the form of study and devotional readings, or 'Parayans,' performed by both the writer of the biography and the broader congregation of devotees who engage with the text. Many devotees have served their Gurus in this second manner.