Unable to get xml array

Hi Friends,

 Dim str As String = "<?xml version='1.0'?><catalog><things><gadgets>Watch</gadgets></things><book><Novel><price>10</price></Novel><Novel><price>15</price></Novel></book></catalog>"
        Dim catalog As catalog = New catalog()

        Dim serializer As New XmlSerializer(GetType(catalog))
        Using reader As TextReader = New StringReader(str)
            catalog = serializer.Deserialize(reader)
            Dim bookprice As String = catalog.book(0).price

        End Using

Public Class catalog
    Private thingsField As catalogThings
    Private bookField() As catalogNovel

    Public Property things() As catalogThings
        Get
            Return Me.thingsField
        End Get
        Set(value As catalogThings)
            Me.thingsField = value
        End Set
    End Property
 
    Public Property book() As catalogNovel()
        Get
            Return Me.bookField
        End Get
        Set(value As catalogNovel())
            Me.bookField = value
        End Set
    End Property
End Class

Public Class catalogThings
    Private gadgetsField As String
   
    Public Property gadgets() As String
        Get
            Return Me.gadgetsField
        End Get
        Set(value As String)
            Me.gadgetsField = value
        End Set
    End Property
End Class

 Public Class catalogNovel
    Private priceField As Integer
   
    Public Property price() As Integer
        Get
            Return Me.priceField
        End Get
        Set(value As Integer)
            Me.priceField = value
        End Set
    End Property
End Class

I am getting error "Index was outside the bounds of the array.

How to get both prices.

Thanks in advance.