According to this article in Britain that's true, 32% of people who bought Harry Potter books had no intention of reading them.
I think this statement is somewhat unclear. From another report about the same data (
http://www.radionz.co.nz/news/latest/200703111756/best-sellers_go_unread)
Just under a third (32%), of adult readers admitted they did not get to the end of Harry Potter and the Goblet of Fire.
32% of adult readers not finishing the book, and 32% of people having no intention of reading them have two totally different meanings.
I could see some people buying the Harry Potter books simply as something to sit on the shelves. It might not happen so much in the US (Since I think there is still somewhat of a stimga associated with adults who read and enjoy these books) but in England I think it makes a lot of sense.
I could also see a lot of adult readers attempting to read the book, and not finishing it. This would really hold true for people who bought it to see what the hype was about, and didn't read (or enjoy) the first 3.
I'd be curious in finding the original source of the information to see if it's broken down or specified further.
I know that personally, I have bought books for "decoration." Such as buying all 6 HP hardcovers. I already have at least one copy of the other 6, but thought it'd be nice to have a 'virgin' set that I could put on display. I also bought a hardcover copy of Elantris that I might not read, that I simply bought after I read the paperback.