How can a devotee offer service to their Guru through literary works, according to the preface?

According to the preface, a Sadguru accepts two main types of service from devotees through books. The first is when the Guru themselves creates a great work, like the Shri Dnyaneshwari. The second, more common for devotees, is to have biographies written about the Guru. As explained in Chapter 0, devotees can offer service by writing these biographies, and the broader community of followers can then offer service by studying them and performing devotional readings, known as Parayans. The Shri Sai Satcharita is presented as a prime example of a devotee-written biography that facilitates this form of service.