David Wells in general

The Penguin Dictionary of Curious and Interesting Geometry - ...

Mathematics is an ocean in which a child can paddle and an elephant can swim. Or a whale, indeed. This book, a sequel to Wells' excellent Penguin Dictionary of Curious and Interesting Mathematics, is suitable for both paddlers and plungers. Plumbers, even, because you can dive into some very deep mathematics here. Far too deep for me, I have to admit, but I can wade a little way into the shallows and enjoy looking further out at what I don't understand, because the advantage of geometry over number theory is that it can appeal to the eye even when it baffles the brain. If this book is more expensive than its prequel, that's because it needs to be: it's a paperback, ...

The Penguin Dictionary of Curious and Interesting Numbers - ...

Many people don't see the beauty and excitement of maths, often because they weren't introduced to it in the right way as children. This book can introduce adults and children alike to it in the right way. It starts with -1 and i (the square root of -1) and goes all the way through to Graham's Number, which is so big that you could drive yourself mad trying to grasp just a fraction of it. En route, it introduces topics and ideas suitable for everyone from absolute beginners to the most advanced mathematicians. That is one of the beauties of maths: someone once described as it like an ocean in which a child can paddle and an elephant can swim. Wells discusses odd numbers, even ...