Interesting report. I don't know if I am surprised or not. I do find the methodology a bit dubious though so whether the statistic is valid, I wouldn't like the comment.
For example, when my DSs were little they regularly got books off the HV. If the children surveyed were 9 to 11 then they would have outgrown those but they still may well have had books in their early years when it was more important.
At 9 to 11, a lot of more time is spent on computer so just because they don't have books it doesn't mean they don't read. Increasingly we won't get our information and leisure reading from actual books and that will be more true of the younger generations than us.
There is no comment on comics/magazines. My 11 yr old who has a reading age several years higher than his age reads mainly magazines. He is unlikely to get through a book a week, sometimes even a book a month. I remember very well the school saying it doesn't matter what they read so long as they read something so I think it is more subtle than do you own books.
Any survey where the participants are self selecting would need to be viewed cautiously - the people who respond are those who think there is a problem.
That said, I think everybody realises that reading has to start at home and that the best way for a child to do well at school is to be read to or read at home and that some children don't get this advantage. I don't think this is a new finding though and I would be interested to know if it tallies with standards of literacy. Does the drop book ownership reflect the change in literacy rates/standards?