Sliding friction is one of the oldest problems in physics and certainly one of the most important from a practical point of view. The ability to produce durable low-friction surfaces and lubricant fluids has become an important factor in the miniaturisation of moving components in many technological devices, e.g., magnetic storage, recording systems, miniature motors, and aerospace components. This book presents a broad overview of friction and an in-depth treatment of several fundamental and related topics. It will be useful to all physicists, chemists, materials scientists, and engineers who want to understand sliding friction. The book (or parts of it) could also form the basis for a modern undergraduate or graduate course on tribology. New topics covered in this second edition include nanoindentation, wear in combustion engines, effects of humidity, rolling and sliding of carbon nanotubes, and the friction dynamics of granular materials.