The book seems to ignore many important saints and focuses only on Sai. Why should I trust its guidance when it's so narrow?

The text in Chapter 19 addresses this by focusing on the essence of devotion rather than a catalogue of saints. It emphasizes that the "sense of difference like 'I and Thou' is the wall between Guru and disciple." Instead of looking for specific names, the guidance is to focus on the underlying principles. The book suggests that true spiritual wealth is the goal, reminding us, "'Allah-Malik, Allah-Malik' (God is the Master); there is no other protector besides Him." The guidance is built on showing how to achieve this connection through surrender and undivided attention, which is presented as the secret of the Bhagavad Gita.