In what two ways does a Sadguru take service from his devotees through books?

According to the information presented in Chapter 0, a Sadguru takes two types of service from devotees through the medium of books. The first way is when the Sadguru creates great works himself, with examples given such as Shri Dnyaneshwari or Shri Dasbodh. The second way is when the Sadguru has his biographies written through his devotees. In this case, the Sadguru accepts service from both the writer and the congregation of devotees who engage with the biography through study and devotional readings, known as Parayans.