'Ryden and Pogge have written a text with the goal of covering what every professional astronomer should know about the interstellar and intergalactic medium. They have succeeded brilliantly. This text provides comprehensive coverage of the topics without diving too far into specialist details. The authors' gift for clear writing, combined with a degree of humor and entertainment, result in an eminently readable textbook.' Evan Skillman, University of Minnesota
'Ryden and Pogge have done a remarkable job of covering the esoteric field of diffuse matter between stars and between galaxies in an encompassing and authoritative way, while maintaining an easy and approachable style. I enthusiastically recommend this worthwhile book for teachers and students of the ISM/IGM.' Karen Kwitter, Williams College, Massachusetts