I'm not reading the newest Harry Potter book (don't worry, I intend to, possibly on our family vacation), but it seems like everyone I know is. Seems that's also true for someone at a blog I've started reading and enjoy a lot called Language Log, as this person posted here. The neatest part of the post for me was the link to the "notae variorum" ("notes of variations"--I translated that without a dictionary! from "nota, notae" and "vari-us, -a, -um"--there's a bit of a problem, though, in that "notae" and "variorum" are both plural, but the former, like most first declension nouns, is feminine, but "orum" is the masculine plural genitive ending: perhaps it's really "notae variarum?" Or maybe they don't have to agree, since variorum is a substantive genitive, not used to modify "notae." Actually, that's probably it. But why should variations be masculine? I like them better agreeing).

There are some really interesting differences between the British and American editions of various Harry Potter books. From the strange, perhaps attempting-to-be-PC additions:

(from Harry Potter and the Philosopher's Stone)
British: "...three people left to be sorted. 'Turpin, Lisa' became..."
American: "...three people left to be sorted. "Thomas, Dean," a Black boy even taller than Ron, joined Harry at the Gryffindor table. "Turpin, Lisa" became..."

to the strange complete rewritings:

(from Harry Potter and the Chamber of Secrets)
British: "...A second later, Harry spotted something that made him hit Ron over the hand with his pruning shears... Harry was pointing at the ground a few feet away. Several large spiders were scurrying across the earth.... Harry watched the spiders running away."
American: "...A second later, Harry spotted something.Several large spiders were scuttling over the ground on the other side of the glass, moving in an unnatuarally straight line as though taking the shortest route to a prearranged meeting. Harry hit Ron over the hand with his pruning shears... Harry pointed out the spiders, following their progress with his eyes screwed up against the sun... Harry's eyes narrowed as he focused on the spiders. If they pursued their fixed course, there could be no doubt about where they would end up."

(was that one just rewritten to put in more of a "Western" feel with the Clint Eastwood-style "...with his eyes screwed up against the sun... Harry's eyes narrowed?")

and the sections that would have been disastrous without "translation":

(from Harry Potter and the Half-Blood Prince)
British: "...I got off with McLaggen..."
American: "...I hooked up with McLaggen..."

There are a lot of interesting things: "forwards" turning into "forward," "the" dropping all over the place, "which" becoming "that," "a team of healers... is" becoming "a team of healers... are," etc., in addition to all the obvious colloquialisms getting smoothed over.