TableViewStyle.qml: Unable to assign Object to QString

TableViewColumn {
            title: "Column1"
            role: "self"

            delegate: Text {
                text: styleData.value.title + " " + styleData.value.author
            }
        }

import QtQuick 2.5
import QtQuick.Controls 1.4

ApplicationWindow {
    title: "TableView Test"
    width: 640
    height: 480
    visible: true

    TableView {
        anchors.fill: parent

        property QtObject book1: QtObject {
            property string title: "A Masterpiece"
            property string author: "Gabriel"
        }

        property QtObject book2: QtObject {
            property string title: "Brilliance"
            property string author: "Jens"
        }

        property QtObject book3: QtObject {
            property string title: "Outstanding"
            property string author: "Frederik"
        }

        model: [book1, book2, book3]

        TableViewColumn {
            title: "Column1"
            role: "self"

            delegate: Text {
                text: styleData.value.title + " " + styleData.value.author
            }
        }
    }
}