Illustrator Jim Kay has been lending his prodigious skills to the Harry Potter series; he's illustrated three so far. The pictures are wonderful! I'm glad that Kay doesn't mimic the films. Instead he offers his own unique vision of the magical world. He likes to work from life: he uses real people as models for most of the portraits, and he built maquettes (3D models) for characters like Dobby. You can learn more at his website here. You can find the books here.
My renewed interest in the Harry Potter series coincides with the departure of my daughter for college -- her own version of Hogwarts. I like to think that I'm a better dad than Vernon Dursley, though. :)
Here's an example of the art from volume 1. Kay's Hermione is modeled after Kay's niece, but she also has bushy hair and other features described by J.K. Rowling. I love the graffiti on the door, the cool reflected light on Hermione's face, the way she grips her wand in the middle (not at the end), and above all the intelligence in her eyes.