Based on the classic number from Disney's Fantasia, this is my take on what would happen if Sweetie Belle tampered with a spell far beyond her capabilities. The ensuing chaos forces her to try and stop it before it's too late.

The book was empty. Purely empty. Each page was as blank as the last. There were no words; there was no title. There was nothing but page after page of blank, white paper.

So Twilight reads it.

A secret unknown to any hornless pony, unicorn horns are made of candy. Pinkie Pie found out, and now she wants to try every flavor!

Warning: contains awkward moments and far too much non-consensual horn licking. Proceed at the risk of your horn and your dignity.

Available in Chinese, courtesy of Hell Organist.
Available in Russian, courtesy of boatOV.
Audio Reading by CaptainBron3y.
Second Audio Reading by Kanjigirl.
Featured on Equestria Daily.

Based on this story:
Pegasus Wings Are Made Of Ice Cream
The Taste Of Madness
Lyra's Candy Shoppe
Candy Is Made Of Unicorn Horns
How Many Licks?
To Prevent Horn Decay
Unicorn Horns Are Made of Heroin
Over His Dead Body
A Luscious Loophole
Dr. Doofenshirtz's Sweet Revenge
That Thing We Do
#DealWithIt
Unicorn Horns are...
Unicorn Horns Are Loaded With Calories
Charlie The Unicorn's Horn Is Made Of Candy

Princess Twilight loves literature, and uses her new found royal prestige to host a symposium in Ponyville.

It's all sunshine and skittles until the authors start showing up.

There's a strange, powerful attraction between Canterlot Castle's captain of the guard and a certain princess of the night. What will happen when the two give in and lose themselves to the power of lust?

Cover art is a cool piece of fan-art by LA Crow.

Trixie wows the crowd with her dazzling displays, and mastery of all things magical.

Princess Celestia’s School for Gifted Unicorns is famous across Equestria as a center of academic excellence. Only the best and brightest unicorns are offered places, selected by their academic merit, magical ability and passion for study. To make the admissions process as fair and reliable as possible, all candidates are given three exams by different teams of examiners, who then meet in private to decide which students are most deserving of a place.

Winner of the December 2014 Writeoff competition: Behind Closed Doors.

Here is an arcanum/ Reference guide to all things Equestrian, by Professor Twilight.

Throughout this compilation many special guests shall be helping the good professor.

Some topics that will be covered:
History
Mythical Creatures
Sentient Species
Cutie Marks
Diseases
Plant Life
Animal Life

All of this and more.

After yet another failure to get their cutie marks, the Cutie Mark Crusaders return to their clubhouse in low spirits and no ideas to test out
But after an incident involving a song with a mysterious magic to it, Sweetie Belle finds fate thrust upon her that no one expected.

Note: This has no correlation with the novel by Rosalyn McMillan which I have not, and probably will not read.
And yes, the cover is drawn by me.

Sweetie Belle decides to go gem hunting despite the protests of the other CMC, and knowledge hidden away from the time of Discord. Inspired by purpose, and in part by Let your mane down by D.Notive.