The book “Symmetry, Phase Modulation, and Nonlinear Waves” by Tom Bridges has been published by Cambridge University Press.  A link to the CUP webpage is here.  The book is an introduction to “phase modulation” in conservative systems which generalises the classical Whitham modulation theory to include dispersion and singularities while maintaining universality.  The theory shows how many classical PDEs, like KdV and the Boussinesq equations, have their natural origins in phase modulation.  The theory brings in a wide range of mathematics such as Hamiltonian PDEs, multisymplectic structures, conservation laws, Noether theory, group theory, singularity theory and analysis, and an introduction to the required mathematics is included.  The book includes several examples of the implications of the theory in nonlinear optics and fluid mechanics.