Celestia asks Luna to teach Twilight dark magic. Twilight must pass Luna's class in order to graduate. As Luna develops feelings for her student, Twilight questions which princess she really wants to serve and protect.
(Twilight X Luna)

After an incident between Applejack and Rainbow Dash, the two are finding it hard to communicate with each other. However, when a friend suggests a pilgrimage to help Applejack settle her feelings over memories of the past, Rainbow Dash and Applejack find that they may have to redefine their friendship.

Twilight Sparkle prides herself on following and sticking to her plans, but she isn't as organized as everypony thinks. Her master list, the plan for her life, has an item that she has never been able to check off; and the time has come to fix that. How hard can it be? All she needs to do is go on a date and get a kiss.

Now available in hard or soft cover!

Dismayed after her loss to Chrysalis, Celestia departs the royal wedding reception early, retreating to her royal chambers to console herself with a bottle of wine. Concerned for her sister, Luna soon follows to check up on her...

(Rated Teen for tipsy princesses, and thanks to Junglepony for the cover art!)

After nearly being mugged Twilight turns her considerable talent with magic towards self defense. When a fight with Luna goes farther that either of them wants it to, Twilight will need to find redemption in her new position as Luna's bodyguard and stop a conspiracy that wants to bring back a force more dangerous than either of them.

After Twilight Sparkle discovers a new book of pick-up-lines, she wants to bring her friends closer by complimenting them with cheesy lines.

And it does more than bring them closer...

Twilight awakes from a minor magical accident to find herself dead. She believes she is doomed to wander Equestria for all eternity, that is until she discovered certain ponies could see lost souls like her, ponies like Princess Luna.

First fic, blah blah blah, constructive criticism, blah blah blah, if you favorite it like it blah blah blah, etc...

Cover art isn't mine

Princess Luna's Lunar Stallions kidnap Twilight Sparkle when they see how lonely Luna is, and give her to the Princess as a gift. Nightmare Moon emerges from Princess Luna's psyche during the sleepover. The dark goddess would love nothing more than to have the beautiful mare all to herself, and the resulting chaos forces Celestia to call a psychologist to sort out Luna's multiple personalities.

Mood Wings - Observations on Pegasus Body Language.

When Twilight Sparkle finds this book, she discovers an entirely new field of research. The secrets of pegasus wings lie before her, and she insists on making her own observations on the matter.

How?

Field research, of course.

After Nightmare Night, Luna invites Twilight to tea, and they start spending more time together. Princess Celestia teases Luna about it sometimes.