How does a Sadguru receive service from devotees through the medium of books?

According to the source material from Chapter 0, a Sadguru accepts two primary forms of service from devotees through books. The first way is when the Sadguru creates great works themselves, such as the Shri Dnyaneshwari. The second method, also described in Chapter 0, is when the Sadguru has his biographies written by his devotees. Through this, the Guru accepts service in the form of study and Parayans (devotional readings) from both the writer of the biography and the wider congregation of devotees who engage with the text.