Once Upon A Time is subtitled "a short history of the fairy tale". It's not a chronological history, per se, but looks at different areas. For example, the feminist interpretation of the fairy tale, the people who collected and translated the fairy tales, whether the stories are rooted in reality, illustrations and so on and so forth. In a way, it's a brief analysis of different aspects of the fairy-tale.
Unlike The Irresistible Fairy-Tale by Jack Zipes, I had no problems with boredom during this book. This could be, however, due to the fact that I read a print copy of Once Upon A Time, while The Irresistible Fairy-Tale was in ebook. I like ebooks, but I find that for certain topics, my attention seems to wander away (and those topics tend to be "denser" ones).
While this book is short, it seems to require a wide knowledge of the fairy-tale genre. Authors like Angela Carter and Jack Zipes are referred to quite often (among the host of other authors referred to), as well as a wide array of fairy-tales. However, these tales don't come with a summary (if they did, the book would probably be four times in size), and so, if you don't actually know the fairy-tale, you may get lost. I certainly did, a few times, and it made me want to read more fairytales (I hesitate to admit this, but I've not read Andrew Lang).
In addition, the book focuses mainly on Western fairy-tales. One Thousand and One Nights is mentioned a few times (as an influence), and I'm pretty sure I saw a mention of the Chinese version of Cinderella (maybe?), but other than that, it's rooted firmly in the west. Anyone know a good book that talks about Asian fairy-tales?
I think this book is a summary of the study of fairy-tales. It may be good as a starting or ending point (to find out what to read, or to connect all the dots), but it is certainly not a comprehensive look at fairytales. In fact, I think you should have read at the very least Grimms Fairy-Tales as well as Mother Goose and a few others first, or you may get lost halfway through.