Read the 1949 revised edition. Interesting historical perspective; especially on British views on opera at the time. Interesting that he saw the future as entirely being in English operas and English translated operas for the future. I believe it was like that for a while (and in Australia also) but for many years original language productions dominate (I guess translated surtitles have helped a lot)
Despite the operatic history covered here by Dent, I don't find much else useful about this text. The writing style is dry, riddled with questionable opinion, and confusing to follow. Many chapters begin covering one subject, then change topic dramatically for a paragraph or a page before finding the way again. It is, however, interesting to hear these antiquated views of works that are often held to great esteem in contemporary opera repertoire.