In this second edition, the following recent papers have been added: "Gauss Codes, Quantum Groups and Ribbon Hopf Algebras", "Spin Networks, Topology and Discrete Physics", "Link Polynomials and a Graphical Calculus" and "Knots Tangles and Electrical Networks". An appendix with a discussion on invariants of embedded graphs and Vassiliev invariants has also been included.This book is an introduction to knot and link invariants as generalized amplitudes...