For the record, I have solved this to my satisfaction. This criteria seems to isolate the useless notices for me:
strFileName = LCase(strFileName)
If (Right(strFileName, 4) = ".azw" Or Right(strFileName, 4) = ".mbp") Then
If Left(strFileName, 30) = "personal documents waiting for" Or _
Left(Right(strFileName, 22), 18) = "note-type_pdoc-v_0" Then . . .
My personal document charge limit is set to zero at amazon.com. Maybe if it was set higher, I would get different kinds of notices. Or maybe if I bought content from Amazon I would get different types of notices (I have mostly been reading Project Gutenberg books and other free content).