Book excerpt: Key Features; An original book - not just a collection of reprints - by an expert, and in many cases the originator, in the field; Although most of the important results are derived, the book also discusses in depth the motivation and meaning of these results; The intrinisic beauty of these models and their solution is emphasized throughout the text, in part by unique full-color figures Readership: Advanced undergraduates and graduate students in physics; non-experts interested in exactly solved quantum many-body systems.