I received this as a school book prize, and it's my favourite pop maths book by far. Whereas most of these books by the likes of Ian Stewart and Martin Gardner are tours around areas of recreational maths suitable for the uneducated amateur (and there's nothing wrong with that), this book is an outline of some of the most astounding and beautiful areas of maths, with the downside being that you'd need half a dozen years of intense study to see all the details. In other words, this is the perfect motivation for university-level maths, and so I got it just the right time, although it must be said I was already heavily into maths by that point.
So, this particular copy has been sitting on my bookshelf in Dursley for most of a decade, and remembering it I rescued it on my last trip. It's pretty much every bit as good as I remember. 163 is once again a mysterious number for me, and I have a strong urge to by textbooks on algebraic number theory and analytic number theory. This'll presumably wear off as soon as I see the contents of said textbooks.
Since this is the first edition, I have no idea what's changed in the second. Well... I have some ideas, since some of the problems discussed in the book have since been solved (e.g. Fermat's Last Theorem). I expect it's still an excellent book, or even rather better, since it will now have layman's explanations for the latest advances.