Why is a spiritual book written without Guru's grace considered inferior?

The preface in Chapter 0 explains that a poetic or spiritual book written solely on the strength of scholarship and intelligence, without the element of Guru's grace, is considered inferior. It states that such a work "will not last eternally, and it will never have the qualities of inspiration, grace, or divine gift." The text further elaborates that without these qualities, the book will not leave a lasting impression on seekers, nor will they develop faith or trust in it. In contrast, Shri Sai Satcharita is presented as a "grace-filled (Prasad-janya) book," which is why it is expected to be widely studied and cherished by devotees.