A nice piece, even though it's not your characters. I like the fact that you altered the design of the my little pony style and the facial expressions are good. It gave me a good laugh and the idea works well, even if it's not an inspiring thought. You've copied the colours nicely and you haven't strayed too far from the original design, so their still recognisable.
In short, it's well done funny and is drawn well. The only thing I don't like as much is the background because the colouring doesn't vary much and makes it a little bit dull so try to make it more interesting.
Vision: It reflects the idea of marriage that Shining Armour seems to carry a lot in this fandom.
Originality: I've seen a lot of almost perfectly drawn versions of the ponies, but this is so far away that it's refreshing. The characters are simple, but their expressions are so memorable. It's one of the many reasons I keep coming back to look at this piece.
Technique: Simple but effective. Sometimes, even parodies can be art within themselves. This is one of them. Twilight Sparkle makes some of the funnies expressions that I've ever seen in a comic. Shining Armour is the character that really brings the comic back to Earth(?) and it's really effective seeing them play off each other.
Impact: I wouldn't be back here several times if it wasn't impacting.
Overall: It has flaws (what's with the fire?), but it's endearing for them. Like an innocent puppy, it does some things crudely, but we forgive it because it's so beautifully cute and rewarding.
Looks like Shining Armor is learning the important phrases: Yes dear, of course dear, you're absolutely right dear, You're ALWAYS right dear. Am I right? That's what my dad was telling me to remember when I find a wife. XD
Well, in some cultures you burn an old book like you'd burn a pile of leaves, or a broken piece of furniture. It's just a way of getting rid of something that you don't need\use. Like ... if you cleared out an old shed and found an old novel that had gotten damp in where the roof leaked. You'd chuck it on with the rest of the rubbish.
In some cultures it can be controversial, and some folks might see it as offensive. There were several times in history when people have publicly burned books as a way of symbolically destroying the ideas that they contained. So ... if you burned a book about the civil rights movement, it could be seen as offensive to black people, even if you were just doing it to get rid of some old stuff.
People can be funny about it in my culture. For example, if a newspaper were to print a cartoon like yours. They'd probably have Shining Armor throwing the book into a garbage can, rather than burning it. Because people might complain if he burned it.
The again, I'd have him throw it into a recycling bin or donating it to a charity. Because I'm into recycling. That's just me.