You might not know the name Mary GrandPré or who she is, but if you are a fan of Harry Potter then I guarantee that you know her work. Mary GrandPré is the artist who created all the original cover and chapter art for the American editions of the Harry Potter books.
Mary was one of the few people who was allowed to read each book before it was published.  She would read each book so she knew what was important about the story and each chapter, then she created drawings based on what she had read. After completing several drawing she submitted her favorites to the book editors, who then chose which of Mary's art would be used for each of the published books.
If you pay attention to Mary's art you will notice that there are subtle hints about either the stories (from the cover art) or each chapter (from the chapter art). The hints she provides are never plot spoilers, which is I appreciate.
Interestingly, Mary drew all the art by hand. Most artists today use computers for their art creation so Mary's approach was old school. I love that Mary's art was completely hand drawn and inked. She did a wonderful job, and her art will always be what I think of when I think of the art for my beloved books.
There are limited edition prints of Mary's Harry Potter work that you can buy. Each piece of art is printed on Giclee paper and comes with a certificate of authenticity. Below are all the available pieces of art, and, as you can see, includes drawings that you won't find in the books.
All items are available for sale at a site called ArtInsights Animation & Film Art Gallery, as well as on their store on Amazon. I've included links to both sites so you can decide which site you'd rather buy a print from.
Do you live outside the United States?
Although some items on Amazon can be shipped world wide, you will probably have the best luck with eBay and Etsy. Click here to see how to know if an item from those three sites can be shipped outside the U.S.A., as well as how you can buy items found and have them shipped to you even if the store you buy from doesn't ship to your country.(Clicking this will open a new window so you won't lose the page you are currently on.)