I think--crazy as this sounds--the last time I got teary eyed while reading something (not like, full-blown bawling, mind you, just misty) was while reading a fan-fiction. It was several years ago, so I was still young, and I couldn't tell you what it was or what it was about really, but if I recall correctly, there was something about the character I identified with on a personal level, and the pain they felt hit a little too close to home. This--I think--led me to the realization that someone else understood how I was feeling, enough to portray it accurately, and had possibly experienced the same sort of pain. It can be a powerful feeling, especially as a teen, to realize you're not alone and that someone, anyone, understands you. And I was a really lonely kid, heh.
Other than that, the only time I've cried reading something fictional was from too much laughter. xD Some of the stories I've read were just so bad, they were amazing in their own special way...