First, I'm sure you know that when you buy an ebook from Pottermore, you can transfer it to your Amazon account. When you do that, Amazon will then push out a copy of the ebook to all the apps and devices registered to your account.
But this might take awhile (it did for me), given how much traffic those ebooks are generating today.
I didn't want to wait, so I downloaded a copy and tried to open it in Kindle for PC. It didn't work. I then transferred it to the Polaroid Android tablet I'm reviewing right now and it wouldn't work in that Kindle app, either. But the app did give me a clue as to why it couldn't read the ebook. It showed me the same message that I've seen every time I've tried and failed to read a DRMed ebook on an unauthorized device:
Please remove the item from you device and go to archived items to download it again.
Yep, that is most definitely not the DRM-free ebook we were promised.
Update: So I've heard back from Amazon, and guess what they told me?
All titles that are pushed wirelessly from Pottermore to Kindle, or to other retailer’s eBook services and readers, are DRM encrypted at Pottermore’s request.
So what we have here is an ebook which is DRM free until you push the ebook through one of the ebookstores. Then it stops being DRM free. That is not what Pottermore said at the press conference. You can check any account from any of the press who attended. All reported that the ebooks would be DRM-free.
I'm waiting to hear back from Amazon and Pottermore, but until then I'm going to be downloading the Epub so I can convert it myself. That much vaunted Kindle Store integration isn't worth it, given that the ebook is locked down with DRM.