A/N: I've actually only seen four movies and read three books. I was in the middle of re-reading book one as a good friend of mine gave me some of the series for my birthday and from the little spoiler knowledge I know of everything, this came out. Short and sweet. Enjoy.
Books or Socks?
Dumbledore stood watching Harry disappear again under his cloak and leave. His soft smile faded a little, a sigh escaping his lips. He was sure Harry would realize later that he hadn't told him the truth. Harry was a smart kid. The headmaster wished that his vision into the mirror really was as simple as desiring a pair of socks.
He glanced into it only momentarily knowing it was better to leave. He walked off, shutting the door tightly behind him. He had seen the same thing many times and there was no reason to linger. He knew personally that the mirror lied. It only showed him a happy ending that could never be.
Dumbledore saw a younger version of himself, laughing ... happy ... calling someone over. He then held the hands of another grinning young man. His mirror-self embraced the other person gently ... he saw something that filled him with an emotion even he couldn't quite place.
Striding down the hall, he pushed the thought from his mind and popped a piece of muggle candy in his mouth. He let himself smile again, the cold wave that had washed over him earlier finally receeding. Chewing thoughtfully, he instead thought about the upcoming term. Life was better being lived, not wasted on empty dreams. He headed contently towards his rooms.
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A/N: I wrote this only based on the very limited knowledge I have from spoilers from my HP-knowledgeable friends, and having read some more things on the subject I think that perhaps he'd actually see something entirely different in the mirror but this is a slashy work and it's supposed to be more thought-provoking than anything else. :)