The ROAD TO REALITY, some 1000 pages long, aims to provide a comprehensive account of our present understanding of the physical universe, and the essentials of its underlying mathematical theory. No particular mathematical knowledge on the part of the reader is assumed- the early chapters providing the essential mathematical background for the physical theories described in the remainder of the book. The aim is to convey something of an overall understanding- a feeling for the deep beauty and philosophical connotations of the subject, as well as of its intricate logical interconnections. Clearly, a work of this nature is challenging, but there is enough descriptive material to carry the less mathematically inclined reader through, as well as some 450- 500, mostly hand- drawn, figures. The book provides a feeling for all the key issues and deep current controversies, and counters the common complaint that cutting- edge science is fundamentally inaccessible. The topics covered in this book include: the roles of different kinds of numbers and of geometry in physics; the ideas- and magic- of calculus and of modern geometry; notions of infinity; the physics and mathematics of relativity theory; the foundations and controversies of quantum mechanics; the standard model of particle physics; cosmology; the big bang; black holes; the profound challenge of the second law of thermodynamics; string and M theory; loop quantum gravity; twistors; fashions in science; and new directions.