Really?

Today I was working in the Science Fiction section today when a man wearing a cowboy hat came to browse some books. He seemed to have some sort of mp3 player or walkman on and occasionally would mutter something.
I thought he was singing along with the music.
And of course I was mistaken.
The muttering soon turned into loud, full sentences, such as "Wow, look at this editorial work? How do they get this through the editors?"
I kept glancing to see if maybe he was using a wireless headset and talking to someone on the phone.
Nope.
Then I thought perhaps he was talking to me and I faced him to see if he'd acknowledge his statement.
Again, nope.
Then he continued to speak aloud. He began to comment on the artistic merits of the various sci-fi writers. "This guy is great! This writing is so good! Yeah, I know. So good"
"Yeah, I know"?
He had begun to respond to himself.
After slowly backing away, I found one of my coworkers and told her about the guy and apparently she had seen/heard him in a different section of the store earlier that day. She too thought that maybe he was on the phone, but soon realized he was just a total and complete wacko.
I'm not sure what the ratio of crazy to sane is in my town, but apparently they love to congregate at my store.