In what ways does a Sadguru receive service from devotees through the medium of books?

According to the preface in Chapter 0, a Sadguru accepts two main forms of service from devotees through literary works. The first method is when the Sadguru creates great spiritual works themselves, with examples cited like Shri Dnyaneshwari or Shri Dasbodh. The second, alternative method is by having their biographies written by their devotees. Through this second path, the Sadguru accepts service not only from the writer but also from the entire congregation of devotees who engage in the study and devotional readings (Parayans) of these biographical texts, thereby helping them achieve the purpose of their lives.