Nowadays, with everyone transistorized, it is hard to imagine (sometimes remember) what it was like without a radio. The first components were developed by amateurs fascinated by the notion of wireless communication; the radio fever was channeled to the Navy during World War I, and after the war the Navy almost secured a monopoly. But the amateur impulse to participate was irrepressible: the ether became so crowded with distance-testing signals that the government finally had to adopt some allocation laws. There were struggles over patents, copyrights, payments for performing, over the propriety of commercials, over the tons of fan mail that came pouring in. Announcers went from anonymity to initials to fame (""no other medium had ever afforded an audience this illusion of intimacy shielded by privacy""). Professor Barnouw knows his subject inside-out, and he writes intimately of many of the famous personalities of the radio business: the woes of De Forest; the spectacular rise of the immigrant David Sarnoff; Tommy Cowan, who ""as announcer, always wore a tuxedo""; Kaltenborn, Husing, and Brokenshire; Bernarr Macfadden and Dr. Brinkley; the advocates of educational broadcasting; and the moment when radio passed from infancy to adulthood, FDR's fireside chats, that ""changed the mood of a nation.