According to the preface, what is considered the ultimate form of literary service for achieving salvation, and what are its specific requirements?

The preface identifies a supreme and most certain form of literary service for spiritual liberation. According to Chapter 0, the highest service is to write the biography of one's own Sadguru, undertaken either by the Guru's command or from a deep inner inspiration. This practice extends beyond the act of writing; it requires the author to personally and regularly study the work, performing hundreds of readings (Parayans) and weekly recitations (Saptahs). This must be done with a firm resolve, pure heart, excellent faith, selfless love, and unwavering devotion. This service is described as being of the body and speech and does not interfere with family life.