Historically, quasi-low-dimensional superconductors were considered as the main candidates to observe high-temperature superconductivity. For a disc- sion of the related exotic mechanisms of superconductivity, suggested by W.A. Little and V.L. Ginzburg, see a chapter by D. J´ erome in this volume. Unf- tunately, high-temperature superconductivity has not been discovered yet in quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) organic ma- rials. Nevertheless, very rich and, in many cases, unique physical properties of their metallic, superconducting, charge- and spin-density-wave phases allowed P.M. Chaikin to claim that the first organic superconductors, (TMTSF) X, 2 are probably the most interesting electronic materials ever discovered. Our book welcomes a reader to a fascinating world of exotic condensed matter physics, low temperatures, and high and ultrahigh magnetic fields. It is written by leading experts in the area from USA, France, Japan, Russia, United Kingdom, Germany, Canada, South Korea, Croatia, Hungary, and Switzerland. The book consists of six parts, subdivided into 27 chapters, which contain both the experimental results and their theoretical explanations. The majority of the chapters contain pedagogical introductions and all necessary illustrations to be read separately. Although we concentrate on physical p- nomena, in the most chapters related chemistry and structural aspects of Q1D and Q2D organic materials are also discussed.