It was after midnight, but in Ponyville, the heat of the previous day still persisted.  In the town library, Twilight Sparkle was so uncomfortable in her bed that her coverlet was bunched into a moon and star-riddled pile beside her.  She rolled to her right, feeling for a brief moment a small desk fan across the room whisk the beads of sweat from her backside.  But the fan then sputtered and stopped, and her body was again cloaked in a blanket of heat.  Murmuring under her breath, her eyes blinked open and she lit a nearby candle with her magic.

“Oh no,” she whispered, “why did the Princess extend the summer this long?  It’s only three days until the Running of the Leaves!”

Stretching her legs, she looked toward the table where the candle sat.  Exhausted in the latter part of the day, she noticed once more that she’d forgotten to put a couple books back on the shelves.  On top of the stack sat a volume still partially wrapped in damaged packaging.  Twilight sighed when she remembered how Derpy delivered it to her instead of to Mrs. Cake.  Returning it to the Cakes was now item number two on her checklist for the next day, behind getting a new fan.

Recognizing that reading would probably be the only thing that would get her to sleep, Twilight summoned the book to her, peering under the packaging to look at the cover.  Golden cursive print spelled out the words “The Goddess Within.”  The title only deepened the mystery.

Twilight was curious, but had resisted reading it, worried about an admonishment from the Princess about messing around with other people’s things.  But she so admired the Cakes, their treats and their charm, that the thought of discovering what new desserts they had in store had become a latent obsession, adding to the discomfort of the night.  The Cakes had been on her mind in recent weeks as the rumor surfaced that the two were planning on starting a family of their own.  

At last, she relented.

Twilight shuffled her way up the bed, taking care not to wake Spike, still sleeping in the distance.  A couple movements and she was sitting up, laying on her back, pillows stacked up in a pile behind her.  With a modicum of effort, she discarded the packaging and eased the book open.  As she turned to the first page, she noticed the book had a curious smell that felt alien to the rest of the library.  The first chapter then presented itself, entitled “A Woman’s Pleasure.”

“With all due respect to the Princess,” it began, “within every mare is a goddess.  A goddess of pleasure.  You are designed both to please and to be pleased, and to know the deepest intimacy existence can afford.  And it is all reflected in your appearance.  Your mane, no matter its length; your fur, no matter its color; your flank, no matter its size.”

Twilight was perplexed.  This wasn’t like any cookbook she had ever read, and by goodness she had read quite a few.  But at the same time she was engaged, and at the same time a little more aware of her body than before.

“But the most important feature of your form lies between your hind legs.  It is your marehood.  It is the attribute over which the bloodiest wars have been fought, but has divined inspiration for some of the greatest achievements of ponykind.  It has ensured our survival for millennia as the gatekeeper of physical intimacy.  In order to love, you must love your marehood and respect its awesome power.”

This paragraph confused her.  She never thought much about her marehood - nopony did, except when they went to the bathroom.  And, even then, its existence was as unremarkable as that of the hole just above it.  Both were strictly functional to mares, the source of a momentary unpleasantness which brought them relief and nothing more.  

The release of waste was treated as common knowledge in Equestria, but was never spoken of, not even by her teachers nor in her biology books.  But the lack of information did not make Twilight curious - just thinking of the whole process made her cringe.  Despite her revulsion, she found herself continuing to read anyway.

“Your marehood is not to be ignored or shunned.  It is to be celebrated for the pleasure it stores within it, waiting to be discovered by your touch—or the touch of another.”

Bleh!  Twilight shook her head and stuck out her tongue.  She couldn’t fathom the thought of someone else touching her there, nor why they would want to do it in the first place.  It had dawned on her that this book wasn’t for her, but it intrigued her that the line responded to her thoughts so perfectly.  And so she kept reading, wondering if it would happen again.

“It’s okay that you don’t believe me, dear reader.  I will make you believe.  You will learn the biggest secret to your existence, and will be forever changed by it.”

A tingle shivered through Twilight’s body at these words.  This wasn’t some cookbook or a Daring Do sequel, but something more - much more.  It felt like the words were speaking directly to her, summoning her to act in accordance with its wishes.  And the more she read, the more readily she lay down her defenses and let it take effect.

“I want you to bring your hoof between your lower legs, dear reader, and touch your marehood.  Feel its softness, its shape, and know the power inside you.”

Twilight’s right hoof slid down the front of her sweaty fur before, with only a moment’s hesitation, it finally reached the mark.  As the edge of her hoof touched the cleft of flesh, pleasure spilled into her body, causing her eyes to pinch shut as she cried at the ceiling.  Surprised by the reaction, but relieved that Spike was still asleep, her eyes opened to read the next line.

“Feel your juices begin to flow, the blood rushing to your loins as it takes control.  Know the desire to be entered, to use your body to coax the essence of life until it fills you and creates life.  Knead your pony mound and bring your body to a simmer, climbing ever higher to the moment where there is no world but you, no experience but your own.”

Twilight’s hoof was already swirling around her moist snatch, juices dribbling down the insides of her purple thighs, creating a small puddle on her tail such that it soon funneled its way backward, trickling downward between her asscheeks.  Her mouth watered as her other hoof began to stroke the sensitive fur on the inside of her left leg, feeling her pleasure spike again when she reached a spot near her crotch.  All the while, she was trying to hold back the moans, suffocating them into a sustained whimper.  Consumed by these frightening new sensations, her vision blurred, making it ever harder for her to read the next paragraph of the floating book.

“That’s it, let yourself go.  Learn to succumb to your desire and let it change your body to its will.  In time, you. . .”

Twilight could no longer keep reading.  She cried aloud again, her head bucking backward into the pile of pillows as her hips thrust forward.  

As she stirred her crotch more feverishly, she felt her torso begin to stretch, her hips widening to better accommodate her busy limb.  A peculiar new sensation buzzed about her chest.  Her left hoof lifted itself from her thigh and felt something hard poking from her chest, then another a few inches away.  Slowly, but deliberately, soft fatty mounds rose beneath them, forming breasts that shook with her trembling body.  By then, her hoof was digging deeper into her pussy, her legs trying to unhinge themselves to swing wider and welcome the stiff invader more readily.  

Another pulse shot through her, causing her whole body to lift, the hard nipples on her hand-sized breasts becoming even more taut than before.  It was then she felt the need to grab the nipple, faintly aware that her left hoof had melted and flattened, distending into five digits that eagerly grabbed the breast with eager awareness.  Her other hoof had changed as well, fingers now wriggling deep within her pussy, where a spark inside her suddenly caught fire.

“Uh–un----UNH!!!” Twilight cried as her hand clenched her breast hard, her entire body locking in a curve as her hips lifted several inches above the bed.  

Twilight’s first orgasm hurtled through her changed form, juice splattering in all directions and coating her hand thoroughly.  Another pulse, then another, and still another consumed her as she cried louder still, the world falling away as the sensation continued to attack her every sense.  

With each pulse, her body gradually returned to its familiar form.  Breasts retreated back into her body, nipples disappearing into the fur of her shrinking torso.  Her hand slipped out of her soaking slit and thickened once more into a hoof, the other hand following suit soon after.  In just a few moments, she was lying on her back once again, her pony body reeking of a stench of sweat and her own essence.  The book, which had stood sentinel above her in a swirl of magic, then fell to the bed next to her with a dull thump.

Breathing deep, raspy breaths into her pillows, she jumped when she saw Spike standing there, his dragon eyes staring through hers.

“Twilight,” he said, “are you okay?  You sounded like you were hurt.”

Twilight hurriedly tossed the stained comforter over her, covering the book.  As the blanket fell, a puff of her musky scent whisked outward toward Spike.  He stood surprised, then appeared oddly relaxed.

“N-no, Spike,” she said hurriedly, giggling in between each few words, “I-I’m fine.  I’m sorry I woke you up, I just couldn’t sleep and I got mad—yeah, that’s all—I just got a little mad.  Not a big deal.  No big deal at all.  So, I need to get some sleep now, and you should too, okay?”

Spike looked at her sideways, shrugged, and walked back into the surrounding darkness.  Once out of view, Twilight blew out the candle and slid under the sheets.  There, illuminated by the swirl of magic about her horn, she lifted the book and continued reading.