I can think of a couple that changed my perception(s) (so, accordingly, life), I think. "The Prophet" was one for sure - and even though it's been years since I read it I still recommend it whenever I can. For me, "The Little Prince" by Antoine de Saint-Exupéry became almost a map of things. Part of that was because I read it as a child, liked it enough, read it again as a young man, "got it" ~ and the whole "life through a child's eyes and how it does, or could, translate to life entirely" became clear. The brilliance of simplicity, I reckon. I think "Gulliver's Travels" was the first book I ever read that made me think really much harder than any book had before (but, again, I read that first when I was pretty little - but recall getting that all this Lilliput stuff
just must mean more than what it looked like at first; it did). There was a so-called "girl's book" [don't believe it

] that I finally picked up when I was in my 30's that brought back to light in me a lot of things that get lost in one's mind as they grow older. I was mad at myself for not having picked it up before - that was "A Tree Grows in Brooklyn" by Betty Smith. I also agree that "Mockingbird" was soundly vibrant. "The Messiah" by Richard Bach. Hmmm. It would seem that the books that have really stirred my sensibilities the most are the ones that remind of ideals that threaten to get beaten out of us as we progress through our travels.
But, and I have to admit it, a few Kurt Vonnegut titles (and the like) rocked my world, too

. But the trick there was to see the world with a cynical or sarcastic (but humorous and intelligent) perspective. Maybe the difference between the Vonneguts and the others that I mentioned is that he attempts to make us aware of the lunacy that can be attached to being a "grown up". The other books mentioned had the knack to make me, anyway, aware that maybe growing up TOO much is not only unnecessary but ultimately damaging? Whatever any of these books did for me, I won't soon forget any of them.