Although Curious and Interesting Geometry was recommended to me by a university reading list, its pace and easy delivery is definately suitable for pre uni reading.
As you would expect Wells lists alphabeticaly interesting geometrical facts. Unfortunately his definitions contain too much text, and fairly few mathematical explanations for my liking. There is a list of more mathematical books in his bibliography, though he doesnt often refer to them, making further reading and research difficult.
A book, in my opinion, that has been designed as a nice easy read, and is suitable to encourage any one with an interest in geometery to persue it further.