What are the ways a devotee can serve a Sadguru through books, and how does this help the wider community?

According to the preface, a Sadguru accepts service from devotees through books in two primary ways. The first is when the Sadguru themselves creates a great work, and the second is when they have their biographies written by devotees. As Chapter 0 explains, by studying and performing devotional readings, or Parayans, of a detailed Guru biography, the writer performs Guru service. Furthermore, when other devotees also study and perform these Parayans, the writer gains the merit of serving God in humanity (Jan-Janardan) and public service, helping other devotees achieve the purpose of their lives.