This self-contained text introduces the physics of structurally disordered condensed systems at the level of advanced undergraduate and graduate students. Among the topics are the geometry and symmetries of the structural units used as building blocks of extended structures, the various kinds of disorder, the phenomenology and the main theories of the glass transition, the structure of amorphous systems and the techniques to investigate it, the evolution of system's structure with its size (clusters) and the presence of orientational order in the absence of translational order (quasicrystals). In the second edition, the treatment of the mode coupling theory of the glass transition has been enlarged and connects now to a new section on collective excitations in disordered systems. Special attention has been devoted to nanometer-sized disordered systems, with emphasis on cluster-assembled materials. Questions of what governs the occurrence and stability of quasicrystals, the features of the amorphous to quasicrystal transformation and its reverse transition are discussed. The conditions leading to nano-quasicrystalline phases of technological interest are examined. Throughout the text relevant recent experimental and theoretical results are discussed so as to give readers insight into the currently most vibrant research topics. From the reviews of the first edition: "The text is clearly presented, amply illustrated and has approximately 45 references with an equivalent amount of further reading [...] it provides a fresh viewpoint which makes it well worth careful reading... [and] provides a stimulating and novel coverage of a difficult subject area." Glass Technology.