My Dearest Fidel doesn't glorify Castro as much as it condemns the media. While Howard's letters swoon over Castro, it really shows how the media was in bed with the Communists and by Howard's admission, would push Trotskyist propaganda on the news.
In the end, it is a story of manipulation and how Cuba used the media and their very willing stooges. Mostly, it is about a reporter prostituting herself out for a story.
I take it the author of this piece didn't read the book and based his review on the title or Howard's letters alone?