This is the sort of book I could really have done with when I was picking my university courses: my thought process was basically "I'm good at French and Maths, and my French teacher says a French degree is pretty much useless, so I suppose I'll do Maths." (It turned out St Andrews had a French for Scientists course, so I did a minor in French too. Win.)
This explains what you study in a maths degree, what you can do afterwards, what to expect at university, and generally comes across as a shout-it-from-the-rooftops of why maths is great.
The only thing I think I would have added is a section on reasons someone *shouldn't* study maths (it isn't a good choice for everyone, and we ought to acknowledge that.)
Overall, excellent.