I thought ancient religious texts were only about abstract spiritual knowledge. Aren't biographies of Gurus just a modern idea?

The provided text distinguishes between purely spiritual knowledge texts and Guru biographies, noting that the tradition of writing a Guru's biography is, in fact, very ancient. Chapter 0 mentions that this service is referenced in the Narada Purana, leaving no doubt about its antiquity. These biographies are described not as abstract texts, but as reliable and true books detailing the Guru's incarnation, life stages, wonderful plays (Leelas), and miracles. Thus, while knowledge texts exist, the practice of biographical writing is an ancient and distinct tradition.