Ok here is the lowdown:
The first book has the most changes, the obvious being the change in the title. The second and third have a few less. By the fourth book the changes are often minor (mostly the use of Kings English vs American English) as the books were published simultaneously by then.
What I find most offensive is that the American publisher does not give American kids credit for understanding British English. Sometimes entire sentences are changed. The American publisher changed the title of the first book because they thought American kids would be confused? Huh???
For example:
On the first page of the third book:
Harry is using a 'torch' in the British book when he does his homework under the sheet.
Harry is using a flashlight in the American book. Brits call a flashlight a torch.
For a list of the changes check out:
http://www.hp-lexicon.org/about/books/differences.html
BTW there is also a Latin version of the Philospher's Stone and it is available in the US from
amazon.
And in the UK they published adult versions of the books. These are the same books as the children's with more adult looking covers so adults could read them on the train commuting, etc. I did get all of these. For example, The Philosopher's Stone has a real steam engine on the cover.
Again - have fun tonite!!!