Can you elaborate on the two types of service a Sadguru receives from his devotees through books?

The Sadguru takes two kinds of service from devotees via books, as detailed in Chapter 0. The first type is when the Guru authors a great work directly, with examples given such as the 'Shri Dnyaneshwari' or 'Shri Dasbodh'. The second type of service is when the Guru inspires devotees to write his biographies. Through this second method, the Guru accepts service in the form of study and 'Parayans' from both the writer and the wider congregation of devotees who read the work. This allows the merit of service to be shared among the community.