The Shape of My Early Life is a partial autobiography describing Lewis' conversion to Christianity. The book overall contains less detail concerning specific events than typical autobiographies. This is because his purpose in writing wasn't primarily historical. His aim was to identify & describe the events surrounding his accidental discovery of & consequent search for the phenomenon he labelled "Joy". This word was the best translation he could make of the German idea of Sehnsucht, longing. That isn't to say the book is devoid of information about his life. He recounts his early years with a measure of amusement sometimes mixed with pain.
