Unique is the right word for this one. I would add engaging as well. The author writes in a style that is less "let me teach you something," more "this is what you should consider if you have an interest in diving, and you should also think about this and this." It encouraged me to continue my learning and training, regardless of how far off that next scuba trip seems to be. I don't know that I would recommend this to anyone before they got their certification, but definitely after.