What does the text say about Guru biographies that were either unpublished or not widely known?

The Preface, as documented in Chapter 0, mentions a couple of such works. It recalls a detailed and scholarly Guru biography written by Shri Samarth Sadguru Tembhe Swami, also known as Vasudevanand Saraswati Maharaj. However, this book had not achieved the same level of fame as the biography by Shri Saraswati Gangadhar. The text also notes that there was another Guru biography written by Shri Samarth Sadguru Dattatreya Maharaj of Balekundri, but at the time of writing, it seemed that this particular work had not yet been printed or published, making it inaccessible to the public.