The text mentions two ways a Sadguru takes service through books. Can you elaborate on these two methods?

Chapter 0 of the preface clarifies the two types of service a Sadguru accepts from devotees through books. The first method is when the Sadguru creates great works themselves, with Shri Dnyaneshwari and Shri Dasbodh cited as examples. The second method involves the Sadguru having their biographies written by devoted followers. In this case, the Guru accepts service in the form of study and Parayans from both the author of the work and the entire congregation of devotees who engage with the text, which is the case with the Shri Sai Satcharita.