The source material mentions 'service through books'. Can you explain how a devotee can serve Sai Baba this way?

According to Chapter 0, a Sadguru accepts two primary forms of service from devotees through books. The first is when the Guru creates a great work themselves, such as the Shri Dnyaneshwari. The second, which is relevant to Sai Baba, is when the Guru has his biography written by a devotee. In this case, Annasaheb Dabholkar wrote the Shri Sai Satcharita. Service is then performed by both the writer and the community of devotees who engage in the study and devotional readings, or Parayans, of that biography. This collective engagement is considered a profound form of service to the Guru.