Just upgraded to Xcode 5. Running the code from the book results in the message: “iOS Simulator failed to install the application.”
Try closing the simulator. I believe you get this message if the app you are trying to install in the simulator is unresponsive to being shut down.
If that fails, delete your app from the Simulator and try again. It’s exactly as you’d expect: click-and-hold to enter jiggle mode, then click the little (x) to nuke it.