This new edition covers the main properties of nematics, cholesterics, and smectics and columnar phases, particularly the symmetry and the mechanical and optical characteristics of each phase. The latter includes some applications to display systems. De Gennes won the 1991 Nobel Prize for Physics. New chapters describe the main types and properties of liquid crystals in terms of the new phases discovered since the middle of the 1970s, and advances in the understanding of local order and the nature of the isotropic to nematic transition. There is an extensive discussion of the symmetry, and macroscopic and dynamic properties of smectics and columnar phases and their defects, illustrated with numerous descriptions of experimental arrangements. The final chapter is devoted to phase transitions in smectics, including the celebrated analogy between smectic A and superconductors. Throughout the book there is an emphasis on order-of-magnitude considerations.