I approached this book with three questions in mind. Being mathematically trained I was curious about whether these really were ideas I didn't know about and needed to. On the other hand I thought about my past students embarking on their training - could they benefit from knowing these 50 ideas? Finally, I wondered if this book might inspire someone to begin to study mathematics, much in the way I was inspired as a novice by trying to read about relativity and finding myself staring into the face of a strange and enticing mystery. The answers were appealingly affirmative, which made me wonder what else it is about this little book that makes it so attractive. Yes, the layout is good with topics mainly restricted to bite-size 4-page spreads. Yes, the hand drawn diagrams give the book a friendly feel and, yes, 50 is a nice round number. But its real appeal lies in the way the author slowly wins the reader's trust and confidence. The author, as tour guide, is friendly and humorous, knows his stuff and communicates it well. In fact, the book is a Pandora's box of delights ranging across an extraordinary wide set of ideas. For instance, ideas 23 to 28 are listed as `Topology', `Dimension', `Fractals', `Chaos', `The parallel postulate' and `Discrete geometry', to list just a few of the enticing mysteries on offer. It is the sort of book I will return to again and again to extract new gems of mathematical insight or historical perspective. But it seems to work also at many levels - I have even had 14-year-old students read and enjoy parts of it. Remarkably, age and experience do not seem to be barriers, though I am always bound to look at it through possibly more practised eyes. Still, I feel completely confident in recommending it, especially to students either setting out on their mathematical studies or thinking about doing so.