are there any differences between the British version and American version of Harry Potter series ?

The differences are pretty minor

http://www.hp-lexicon.org/about/books/differences.html

You can check the links here to find all the differences. Personally, I think they wasted their time. I suspect only the very young readers would have been confused by the original British words.

Jim, http://www.life-after-harry-potter.com

the covers are usually different, but thats about all i know.

The covers and the title of the first book. Instead of "Sorcerer's Stone" it's "Philosopher's Stone" in the British version.

Don't know why they changed it, really.

The main difference is the spelling and terms they have used:

British version - American Version
moustache- mustache
neighbours-neighbors
gray-grey
get-ups -getups
car park- parking lot
lunch-time- lunchtime
baker's opposite-bakery
dialling -dialing
realised - realized
passers-by -passerby
behaviour- behavior
Shan't -Won't
living-room -living room
news reader-newscaster
Yorkshire-Yorkshire,
lot - crowd
bright-bright,

hope this helps!!

Well of course there's the title of the first book - that it's the Philosopher's Stone in England, and the Sorcerer's Stone here.

Hmm.. aside from the cover itself, the size, and the plot summary in the cover flaps (for hardbounds), I don't know, maybe if there are some, you could hardly recognize the difference at all. Maybe some words in British are gives a different connotation and denotation as well in American English so she has to make some changes, and vice versa..

In the American one they say realize with a 'Z' but in the English one they say it with a 'S'.

I've actually wondered about that. Good Question!