What is reading?

I was listening to the audiobook of Barack Obama's The Audacity of Hope this morning on the bus, and I thought Is this reading?

My immediate thought was no. Reading has to have words printed on a page. Then I thought of Shaun Tan's The Arrival, which has no words, but is definitely read.

But you don't read a painting in a gallery. Do you?

You do read:
-sheet music

Wikipedia says: Reading is the cognitive process of deriving meaning from written or printed text. I am not so sure.