Pottermore launched their ebookstore today, and you can now also find Harry Potter eBooks in the Kindle and Nook eBookstores. The eBooks are sold via Pottermore, not Amazon and B&N, so you’ll first need to set up an account with the site.
Once you’re there, you’ll find that you can buy the eBooks and then download them in Epub format. But if you want Kindle, you’ll need to convert the Epub yourself or transfer the eBook to the Kindle Store. Prices start at $8 (for the first 3 books in the series), and the last 4 titles cost $10. You can also buy them as audiobooks. And after you buy the eBooks, you have the option of transferring them to your account in the Nook, Kindle, Google Play, or Sony Reader Stores.
I wouldn’t transfer the ebooks just yet. Early reports suggest that not all the bugs have been worked out. While the eBooks can be transferred to the Kindle Store, the one I bought won’t open in any of my Kindle apps. I’m still waiting for the Kindle tech support to fix it.