This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169

Book II
Brought out of the darkness of solitude and into the light of friendship, Dusk returns once more to see and learn just what magic and wonder friendship has in store for him. Once thinking he was the most useless, pointless pony to ever exist, he has now found those who care for him and appreciate him for who he is, opening up new possibilities never even considered.
He will join the girls on their adventures and experiences with friendship’s magic, helping them along as they go, having a few of his own and learning and discovering new aspects of himself that become open now friendship is known to him. Along the way, he will also make new friends, challenge his own beliefs and convictions once more and just discover how much more wonderful life is with friends as a part of it.
But that’s not all that concerns him here. He needs to do something different about himself, but what? He has his colour magic, but where exactly did it come from and are there others he shares it with? Twilight may be his best friend but… what’s this new feeling that he has when he’s around her now?
All of this will be explored, as Equestria prepares to see a brand new Dusk.
Cover again by Quillin Words.

Book I
Meet Dusk Noir, a unicorn stallion from Canterlot. He attends Princess Celestia's School for Gifted Unicorns, has a liking to learning and reading and has a unique magical talent. He seems like he would be happy, but there's just one problem: he doesn't have any friends. It's not that he doesn't want them, but he just feels that he wouldn't be worth the time of anypony. He sees himself as unremarkable, a waste of space and not much to bother with. There's only one pony he'd even consider being good enough as a friend for and he doesn't even know how to say the first word to her. It seems like he will always be alone.
Until one night, when he discovered by the Princess of the Sun and is sent to Ponyville to meet her at last. Can he achieve the goal of earning her friendship and much more besides or will he be simply left alone?
This is a story that I began as a sort of creativity outlet when I discovered how much of a fan I was of the series. From there, it just kind of grew and I enjoyed continuing it. Doubtless, you probably know what it's going to be about before you even read it and would even be tempted to point it out. I won't try and change what you think, all I ask is that you give it a chance.
There are two more stories following this, both of which along with the fuller version of this one, can be found on my fanfiction account. Just search my username and you'll find them, if you really want to read more that is. I'll try posting on as regular a basis as I can. That is, if it's received well.
This first one isn't my best, I'll admit that much, but I certainly did try my best with this one and what I had planned for it. I hope you enjoy it.
The cover was by Quillin Words and he did a fantastic job, thanks dude!