What are the two ways a Sadguru accepts service from devotees through books, as described in the source text?

Based on the details provided in Chapter 0, a Sadguru takes two distinct types of service from devotees through books. The first method is when the Sadguru creates great spiritual works themselves, with Shri Dnyaneshwari and Shri Dasbodh cited as examples. The second method involves the Sadguru having their biographies written by their devotees. In this case, the Sadguru accepts service in the form of study and Parayans (devotional readings) from both the writer of the biography and the wider congregation of devotees who engage with the text, thereby helping them achieve their life's purpose.