To understand this book, you have to consider it in context. Helen Keller is not telling the "story of her life"--how could she? She was only 22 when she wrote it. She is telling the "story of my life up to this point." Keller was a student at Radcliffe College when she wrote this autobiography, and it is not the last one she would write. She came out of dark isolation into a world of learning and language--well, into the world. At this point, she has friends and studies and a full life, and as a student at a preeminent college, she has reached the highest level of success thus far--and much higher than anyone would have thought possible a decade earlier.
With this information in mind, it is easy to see and understand the joy in this book. The message is one of appreciation and self-congratulations. To steal a little from Walt Whitman, she is "singing the song of herself." She writes about the skill of her teachers, Anne Sullivan, the help of her friends, and her own progress in tones of wonder. The message is--you can overcome. Anyone can overcome, because look at what Helen Keller achieved.