JK Rowling is late to the ebook game. And she still has not really bought into it completely. But it is now possible to get the Harry Potter books on your kindle legally. It is not as easy as it should be. But Rowling has created her own store, requiring a you be redirected to the Pottermore site and then buy it there.
What I do like is that you buy it at the Pottermore site and it is available in multiple formats (readable both on Kindle and Nook and other ebook readers.)
So you go to Amazon, Click on the book you want. Then you get forwarded to the Pottermore store, then you confirm the book, create an account (or log in if you have already created an account), then pay for the book. It is outside of Amazon, so you can’t use Amazon gift cards. The store also does not accept American Express or Discover. I keep a secure file for my credit card numbers so I can cut and paste them in forms. The checkout procedure prevented me from pasting my credit card number in.
I was also forced to enroll in a verified by visa program and give the last 6 digits of my SSN, my billing zip again and the expiration date (which I already entered.)
Then you link your Amazon account to your Pottermore account (just logging in again) and your book appears in your Kindle Account. (You can also download the book and email to your kindle account to do the same thing.)
I could not find the Amazon links to the Harry Potter books without the direct link. I would guess that it will be easier to find eventually.
Just looking at the above picture makes me wish I had been able to buy the kindle versions originally. I have more than one copy of most of the hardcovers (because my wife and I both wanted to read them as they came out.)