The story here is quite frankly, secondary. What a curious thing to say about a book, but it certainly fits with "Rarity and the Curious Case of Charity". Rarity is the fashionista pony, she's an Equestria famous dress designer, and an eager young student is sent to her Ponyville residence for her to apprentice in the ways of making Rarity quality dresses. The young starry eyed pony gets caught up in hero worship and takes her idolizing to damaging levels, culminating in a rather typical... ahh... "fashion". It's pretty standard stuff. Animate it and slap a few songs in there, and you would have a decent filler episode of "Friendship is Magic".
HOWEVER the story is not the reason to read this. If you love the ponies, and want more time with them while waiting for the next season of MLP:FiM to air, then this book will do the trick, at least for the span of nearly an hour. The characters are written brilliantly. Every mane toss, conversation, and situation sticks completely true to the characters. Their banter is so on point that you can visualize them talking and hear their voices in your head. There is no wonder why the kids enjoy this pony book series so much, reading one is like hanging out with your favorite four hoofed friends for awhile, and that's a very cool thing.
The story is average, but has a good message, and the book is full of that ponyfied flavor. Little fans of MLP will enjoy this, and you can feel about them reading it. Older MLP fans might want to take a look too, it's perfect light fluff to read while in a waiting room. Adults do a lot of waiting, why not wait with some pony friends?