What are the different ways a devotee can serve a Sadguru through books?

According to the preface in Chapter 0, a Sadguru accepts two primary forms of service from devotees through books. The first is when the Sadguru is a great author themselves, creating works like Shri Dnyaneshwari. The second, more common method, is when the Sadguru has their biographies written by devoted followers. In this case, service is rendered through the study and performance of Parayans (devotional readings) of these biographies. This form of service involves both the writer, who performs Guru service through the act of writing, and the congregation of devotees who study the work, thereby helping them achieve the purpose of their lives.