That cannot possibly be determined.
As of 2008, over 400 million copies of the books had sold. This is not an accurate number because the owners of these books may not have completed them, they may have shared them with friends and people have borrowed books from the library. There are also audio-version of the books and illegal e-books floating around. Some people will also have read it or have had it read to them in school.
While an accurate number cannot be determined it is safe to say that millions have read them.
Love and adventure losers
Eight. In the last film, Harry is seventeen and she is twenty-five.
No, it is not. Harry himself is a Horcrux, because Voldemort had rendered his soul so unstable by murdering so many people that the piece that had torn off with the murder of Harry's parents (Lily and James) latched onto the last living thing in the house, which just so happened to be Harry.
None.
7 books 8 movies (last one is two parts)
28
6 decoys, so there are a total of seven Harry Potters.
717,020
7
There is only one Harry Potter, and he doesn't die in Azkaban.
Two: Joe and Paul DeGeorge
about 22 if your counting Hedwig
Love and adventure losers
No one, but they have been translated to Chinese.
Ginny is in every Harry Potter and plays a main part in the second, fifth and seventh films.
There was seven books, three additional books and eight films.
There are no light bulbs in the wizarding world.