According to the preface, how does a Sadguru like Sai Baba utilize literature to accept service from his followers?

The preface to the Shri Sai Satcharita explains that a Sadguru accepts two primary forms of service from devotees through books. As detailed in Chapter 0, the first is when the Guru creates profound works themselves, like the Shri Dnyaneshwari. The second method, which applies to Sai Baba, is having his biography written by a devotee. The Sadguru then accepts service from both the writer and the wider congregation of devotees in the form of dedicated study and devotional readings, known as Parayans. This act of engaging with the Guru's biography is a key form of service that allows devotees to connect with him.