The book at least follows a cohesive plot and story, which already place it above Phantastes. It tells the story of a princess, Irene, and her friend Curdie. Irene has been selected by the goblins to be kidnapped in their plan to take over the Abovegrounds. Curdie, a miner, is the only one who hears of their plans and the only one who can stop them. Along the way, Irene is aided by her grandmother (An interesting character who, in true MacDonald fashion, is left infuriatingly unexplained).
I will say one thing: MacDonald's actual writing does not lack. Thankfully, when coupled with a fairly good plot as this one, the book is actually somewhat enjoyable. The real litmus test exists when there is a sequel (The Princess and Curdie). Since I look forward to reading the sequel, I have concluded that this book was a good book, overall. It kept my attention and though it dragged a little, let's remember it was written in the 1800s.
Overall, I'll adjust my former rating of MacDonald to the fact that he's a pretty good writer, but in my opinion there's other writers that do the same thing so much better. Still, to be fair, MacDonald was one of the pioneers of the fantasy genre. So, if you're interested, I'd definitely recommend you give this one a try over Phantastes.