The preface discusses how a Sadguru receives service through books. What are the two distinct forms this literary service can take?

The preface, in chapter 0, outlines two specific ways a Sadguru receives service from devotees through literary works. The first form of service is when the Sadguru themselves authors a great spiritual work for the benefit of humanity, with texts like the Shri Dnyaneshwari or Shri Dasbodh serving as examples. The second form of service is when the Sadguru inspires devotees to write their biographies. In this case, the Guru accepts service from the writer who creates the work, as well as from the wider congregation of devotees who engage with the biography through study and performing Parayans, or devotional readings.