Harry Potter and the Sorcerer's (Philosopher's) Stone
Even with the first set of book covers, it becomes apparent that the UK has made more of an effort to tailor the book covers to attract children and adult readers. The US cover seems to try to appeal to audiences by including a items and snippets of scenes from different parts of the book in one illustration. Both the UK children's cover and first edition of the adult cover both feature the Hogwarts Express, and obviously the children's cover is cartoonish, while the adult cover doesn't hint at anything magical at all and doesn't include any characters from the book. The second adult edition of the Philosopher's Stone simply illustrates the title by showing the stone in red, a departure from the first edition's black and white format.
Harry Potter and the Chamber of Secrets
Both the US and UK children's covers are fairly friendly in appearance and almost comical; the use of bright colors is consistent, while the US cover is much more cartoonish than the children's cover from the UK. Like the first book, the UK's children's cover and the first edition of the adult cover use the same theme, vaguely mirroring each other with the image of the Flying Ford Anglia in the clouds. However, the adult cover uses a black and white color scheme and does not include Ron and Harry within the car, perhaps to suggest that the story can be enjoyed by adults despite it's focus on juvenile characters. The second edition of the adult cover is even more vague, and, like the US cover, features an image from the end of the story rather than the beginning.
Harry Potter and the Prisoner of Azkaban
Harry Potter and the Prisoner of Azkaban is the only instance in which the US, UK children's edition, and first edition UK adult covers all contain the same imagery: a hippogriff. Obviously, the US version is the most cartoonish, but it parallels the UK children's version most closely because both covers display Harry and Hermione riding Buckbeak. Although the US and UK artists did not collaborate on their illustration decisions, they both clearly thought that this scene was crucial to the plot and necessary in conveying the story's theme. While the first edition of the UK adult cover is consistent with the children's cover, it displays a more realistic, black and white hippogriff that sort of looks like a half-assed Photoshop experiment. The second adult cover is the most somber of all, with an image of Azkaban Prison on in its isolated environment.
Harry Potter and the Goblet of Fire
In this cover illustration, the US artist created a collage of different characters, items, and events from the story to convey the adventurous spirit of the book. The children's and first edition adult covers from the UK both feature a dragon that harry fights in one of the Triwizard Cup tasks. Both of the dragons are mildly scary, although the adult cover's book displays a dragon that does not nearly fit the description of the Hungarian Horntail from the book. At this point, it's clear that the second edition of the UK adult covers try to display a literal and direct representation of the book's title; fittingly, the fourth book's cover displays the Goblet of Fire.
Harry Potter and the Order of the Phoenix
This is the first series of covers in which both UK versions feature the same content. Although a phoenix isn't a prominent feature of the story line, the phoenix presented on the covers effortlessly reflect the book's title. The US cover art is significantly more serious than the previous books, and it is the first in which Harry is not smiling. The dark, mysterious shades of blue and distorted shapes are meant to parallel the story's seriousness and the tragedy of Sirius's death that Harry is forced to deal with at the end of the book and for the rest of the series.
Harry Potter and the Half-Blood Prince
Like the fifth book's cover, the US cover for the Half-Blood Prince was created using mostly shades of green, which conveys a sense of mystery to the audience. It's the only US cover in which Harry is not the central figure of the illustration. The UK children's edition also includes an image of Harry and Dumbledore as a united pair; this is most likely to foreshadow Dumbledore's death and draw the audience's attention to Harry and his headmaster's relationship throughout the book. The UK adult edition's cover includes a picture of the Half-Blood Prince's copy of Advanced Potion-Making, which plays an important role in Harry's last year at Hogwarts. The imagery reflects the book's title, again.
Harry Potter and the Deathly Hallows
Both the US covers and the UK children's covers for the Deathly Hallows portray a scene of action. In the US cover, Harry is reaching up to catch the Elder Wand after disarming Voldemort, and the UK children's cover shows Ron, Harry, and Hermione escaping the Lestrange vault in Gringott's. The action depicted in these covers are meant to convey to the audience that this book contains the ultimate climax of the story, making it the most dramatic and action-packed of them all. Conversely, the UK adult cover simply includes an image of Salazar Slytherin's locket, which is one of the horcruxes that Harry and his friends spent the entire story tracking down and destroying. Although it does not directly relate to the title, it is still a pivotal object in the story and draws viewers in because they want to know exactly how it relates to the story.