The preface talks about serving a Guru through books. Can you explain the two main ways this service is performed?

According to the preface, a Sadguru accepts service from devotees through books in two primary forms. The first way is when the Guru themselves creates a great literary work, with examples given such as the Shri Dnyaneshwari or Shri Dasbodh. The second method, as detailed in Chapter 0, involves the Guru having their biographies written by their devotees. In this case, the service is accepted not only from the writer but also from the entire congregation of devotees who engage in the study and devotional readings, known as Parayans, of that biography. This act of collective study is seen as a form of service to the Guru.