This book is totally inappropriate for learning mathematics, especially for a teenager. A well-prepared layman, maybe, but not a teenager who just wants a good introduction to the subject.
It's purpose to me at least was as a guide to the mathematics that was too difficult for me to understand straight away but could be considered the end goal to a given study i.e. As Symplectic Geometry is Analytical Mechanics.
I would be absolutely flabbergasted if a layman could get through Road to Reality. Even those with an engineering or computer science background would struggle considerably.
That said, it serves as a great overview of physics for mathematicians and perhaps as very casual intro to twistor theory for physicists.
