C.S. Lewis is the probably the best writer (particularly theological or philosophical) I have ever read. I don't like when writers feel they have to dumb-down ideas when they try to explain them, and I dislike even more when they show off their superior intellect by needlessly complicating things with weird sentence structure or words that sound learned. C.S. Lewis gives the full picture in stunningly simple terms (he makes writing clearly seem so effortless!), and yet you feel the full force of his intelligence behind it. Even in the Narnia books, it never feels like he's trying too hard.
Now that I think about it, seeming effortlessness is my favorite literary style. Bill Bryson writes "choke-on-your-coffee funny" books, but it never seems like he's trying too hard. And then when I try to write something in the same style I realize how ridiculously difficult it actually is. And then I say what the heck, toss down my pencil, pick up I'm a Stranger Here Myself and vow to leave writing to people who can actually do it.