Einstein's General theory of Relativity is usually thought to be a difficult topic, not approachable by the non-mathematician. However, in 'A journey into gravity and spacetime' Wheeler gives an entirely non-technical account, using the geometrical ideas which are at the root of the subject. With plenty of pictures, and a fair amount of poetry, he uses ideas such as 'The Boomerang Project' - a shaft straight through the Earth, and 'The Boundary of a Boundary', to give an intuitive feel for General Relativity. The final chapter gives an account of Gravitational Waves and discusses the significance of the experiments designed to find them.
I have to say I do have some reservations about the book. To me it didn't seem to have enough of a central thread which would lead the reader on to further study. It's fine if you want to get an overview of GR and aren't intending to go any further with the subject. However, there are no suggestions for further reading, and readers attempting to move on to more mathematical accounts might find that Wheeler's introduction doesn't really help them. For instance he spends much time discussing the curvature of the paraboloid space of the Schwarzchild solution, but in discussing the orbit of an object - a geodesic in spacetime - he abandons the ideas of curvature and uses energetic considerations instead. I feel that an opportunity has been missed here.