I think the only book that's ever made me cry was The Perks of Being a Wallflower.
It's about a boy's first year of highschool, and basically what he see's, hence the whole wallflower thing.
But the a couple of the things that always seem to make me cry are...
xD Before I start quoting the whole book, I'll post the one I was originally going to post..
xD You're probably thinking why would that make you cry? (well aside from the poem, I think it's quite the heart wrenching poem), but I think when you put things into your own perspective, and apply it to your situation(s) anything can be upsetting o.o.