Will we ever discover a single scientific theory that tells us everything that has happened, and everything that will happen, on every level in the Universe? The quest for the theory of everything - a single key that unlocks all the secrets of the Universe - is no longer a pipe-dream, but the focus of some of our most exciting research about the structure of the cosmos. But what might such a theory look like? What would it mean? And how close are we to getting there? In New Theories of Everything, John D. Barrow describes the ideas and controversies surrounding the ultimate explanation. Updating his earlier work Theories of Everything with the very latest theories and predictions, he tells of the M-theory of superstrings and multiverses, of speculations about the world as a computer program, and of new ideas of computation and complexity. But this is not solely a book about modern ideas in physics -- Barrow also considers and reflects on the philosophical and cultural consequences of those ideas, and their implications for our own existence in the world. Far from there being a single theory uniquely specifying the constants and forces of nature, the picture today is of a vast landscape of different logically possible laws and constants in many dimensions, of which our own world is but a shadow: a tiny facet of a higher dimensional reality. But this is not to say we should give up in bewilderment: Barrow shows how many rich and illuminating theories and questions arise, and what this may mean for our understanding of our own place in the cosmos.