This work is devoted to the theory and approximation of nonlinear hyperbolic systems of conservation laws in one or two spaces variables. It follows directly a previous publication on hyperbolic systems of conservation laws by the same authors. While in the earlier publication, the authors concentrate on the mathematical theory of multidimensional scalar conservation laws, in this work, they consider systems and the theoretical aspects which are needed in the applications, such as the solution of the Riemann problem and further insights into more sophisticated problems.