Originally published in 1968, Malone's book was the only game in town for a long time. Many other academic histories of country music have since been published, but this remains the gold standard and still probably the place to go if you want a one-stop, serious resource.
This is an odd and captivating book by a brilliant writer. Nobody writes about country with the style and fervor that Tosches brings to his work. Country is a rock and roll account of country music history, and Tosches has a clear affinity for the most rough and tumble aspects of that story. Particularly exhilirating is his section on Jerry Lee Lewis.
Escott, who has also written a fine biography of Hank Williams, wrote this book to coincide with the production of a BBC series on the history of country. If you're only going to read one book on the subject and don't want to commit yourself to something as long and involved as Malone's account, this is the book to go for, clearly written, well told, and supplemented with fine photos.
Millard's book is a well-organized reference for the fan or researcher. He includes lots of performer bios, great photographs (some of which haven't been published anywhere else), solid interpretive essays, and a year by year timeline of notable releases and events.
On one hand, the Rough Guide is a solid resource for information, a meatier, more nearly encyclopedic reference guide than Millard's. On the other, it may not be as clearly organized and isn't nearly as critically astute as Malone or Tosches. It will however, answer a lot of simple questions of who is who, when, and where in the history of country music.