I've never really understood the fine arts:
What does the subject's smile convey?
What do the background plants represent?
I've never been able to answer questions like these, and have often wondered if the whole industry isn't made of the same squishy, stinky stuff that drives the wine-tasting industry). But after reading Isaacson's biography of Leonardo da Vinci, I now realize that doesn't mean I can't have an appreciation for a true artist.
Leonardo was an inspiration. He innovated in many ways, and not just in the fields for which he is best known. This self-educated bastard* reached the height of renaissance thinking thanks to his own curiosity and perseverance. We know this because he kept a blog, but on paper! And the things on which he ponders are incredible. He advanced a number of subjects, but sadly rarely published anything, resulting in the credit for discoveries often going to others generations later.
It's long though, so if you lack an appreciation for detailed discussion of various paintings, you may want to skim a little, as I admit to having done.
* I'm not judging here. I only bring it up because it was a very real hindrance during the epoch in which he lived.