What is the author's tone in Dark Night of the Soul by St. John of the Cross?

The tone of the book is subjective, as it conveys very strongly the way St. John feels about a soul that that has or is passing through a dark night. During his discussion of the dark nights of the soul and spirit, St. John gives examples of how the soul will feel and what it will experience during its journey toward union with God. Knowledge of these feelings, thoughts and emotions could only come through St. John's own personal experience.