From a Sadguru's perspective, what are the different ways they receive service from devotees through books?

According to the preface in Chapter 0, a Sadguru takes two primary types of service from devotees through books. The first is when the Guru directly authors great spiritual works themselves, such as the 'Shri Dnyaneshwari' or 'Shri Dasbodh'. The second, alternative form of service is when the Sadguru has his biographies written through his devotees. In this case, the Guru accepts service in the form of study and 'Parayans' from both the writer who created the work and the broader congregation of devotees who engage with it, thereby expanding the Guru's spiritual reach and teachings.