Xml Dom Problem passing through all nodes

Attached 3 files
books.xml
xmlDomShowTree.aspx - which contains one label
xmlDomShowTree.aspx.vb - Code behind

i am trying to loop through the xml file with showtree(ByVal node As XmlNode) function the i passing into it xmldoc.DocumentElement object.
in this function i have the 2 declarations

Dim attrnode As XmlNode
Dim map As XmlNamedNodeMap

and map is initiated as

map = node.Attributes

im trying to loop the tree by the folowing loop

For Each attrnode In map
strOutput += "<b>" & attrnode.Name & "</b>&lt;" & attrnode.Value & "&gt;" & vbCrLf
Next

and it doesnt enters the for each loop - why is that??
thnks