The provided text states a Sadguru takes two types of service from devotees through books. Can you describe these two types of service?

The source material explicitly mentions that a Sadguru takes two distinct types of service from his devotees through the medium of books. However, while Chapter 0 states this fact, it does not proceed to describe or elaborate on what these two specific types of service actually are. The text in Chunk 7 concludes with the sentence, "The Sadguru takes two types of service from his devotees through books," but the provided excerpts do not offer any further details on this point, leaving the reader to understand only the existence of this concept without a full explanation.