The source mentions two types of service a Sadguru takes from devotees through books. Can you elaborate on these methods and how they apply to Sai Baba's legacy?

Chapter 0 outlines two ways a Sadguru accepts service via books. The first is when the Guru themselves authors a great work, like Shri Dnyaneshwari. The second method, which is directly relevant to Sai Baba's legacy, is when the Guru has their biography written by a devotee. This biography is then used for service in the form of study and Parayans by both the writer and the wider congregation of devotees. The Shri Sai Satcharita, written by Annasaheb Dabholkar, perfectly exemplifies this second form of service, allowing the community to connect with Sai Baba through the dedicated study of his life.