Based on the preface, what are the two main ways a Sadguru accepts service through books, and which category does the Shri Sai Satcharita fall into?

The text in Chapter 0 outlines two distinct ways a Sadguru accepts service from devotees through literary works. The first is by creating great works themselves, like the Shri Dnyaneshwari. The second method is by having their biographies written by their devotees. The Shri Sai Satcharita is a clear example of this second category. As Chapter 0 explains, the Sadguru accepts service through the study and Parayans of such a biography, performed by both the writer and the congregation of devotees, making the book a medium for devotional service.