The following excerpt from the audio version of the book (read, as usual, by Dawkins himself and Lalla Ward) explores the kind of question that a young inquiring mind might ask her parents: who was the first person really?
Dawkins provides a wonderfully clear explanation not only of the answer but of the thought process required to try to come to grips with the significance of such a question. The greatest accomplishment, I think, is that the very same excerpt can be understood by children and it can stimulate adults to think about some of the philosophical implications of the answer, such as the sorites problem of what a species really is if no one's parents are ever members of a different species... and yet most of our ancestors do belong to different species.
Maybe I'll have to end up getting a copy for myself too :)
Update: Here's Dawkins briefly explaining what the book is about