From OverDrive’s site:
We’re excited about the forthcoming launch of Harry Potter eBooks and digital audiobooks for library lending. We’re working with Pottermore to introduce this compelling series, and as part of the process of coordinating launch plans with Pottermore, we have temporarily suspended pre-sales and display of these titles at library websites. This is only a postponement, and libraries will soon be able to resume pre-ordering the titles in preparation for launch in April.
We apologize for any inconvenience and appreciate your understanding. We’ll keep you posted as the process unfolds.
But wait, is there more? eBookNewser’s Nate Hoffelder speculates that OverDrive may be having server problems due to the popularity of the Potter books (OverDrive Halts Advance Sales of ‘Harry Potter’ Library eBooks):
This is a curious turn of events, but I suspect it is due to a technical issue. I bet OD’s servers were beginning to get bogged down by the requests for info about the eBooks.
Read more at eBookNewser.