Lonni Sue Johnson developed severe amnesia after a terrible bout of encephalitis. It took out her hippocampus and although she regained motor and speech functions, most of her episodic memory of the past was gone, and she was unable to form new memories.
The book explores her case, her life, and what researchers have discovered about brain function through studying her case. The book also provides a shorter, similar presentation on "H.M.", a previous case that allowed scientists their first good look at the connection between brain and memory.
Lonni Sue was distinguished in a number of ways. She was a professional artist, an accomplished violist, and a trained pilot. Some of the more interesting experiments established that her procedural memory was in some ways intact, even in cases where she wasn't consciously aware of it. The experimenters had 3 viola pieces composed of roughly equal difficulty. After she was exposed to them all and sight read them, some were chopped up into pieces for her to 'practice'. Although the piece of music was always new to her each time she saw it, she was better able to perform the ones she had 'practiced'.
The book spends a bit too much time fleshing out the biographical details of Lonni Sue and her family members (and H.M.) but at least in her case it develops a very sympathetic portrait of a person. And while her cheerful personality exists, it's clearly trying for her friends and family. Her friends she largely doesn't know at all, while her sister has to remind her of the (long past) death of their father over and over again.
Another interesting detail is that she was introduced to word search puzzles, and somehow this fired off something in her creative brain and it's become something of a monomania for her. She creates, yet never quite completes, word search puzzle presentations over and over again. Typically with a theme and decorated with her artwork. In some way, it seems these have become a new way for her to organize and understand the world. All the words are there on the page... no need to try juggling them in memory.