Author J K Rowling has completed her sixth book about the boy wizard 'Harry Potter'.

It is called Harry Potter and the Half-Blood Prince.

"I know you all expected this to happen on Christmas Day, but I was sure that those of you who celebrate Christmas have better things to do on the day itself than fight your way into my study, whereas those of you who DON'T celebrate Christmas would definitely prefer not to wait until the 25th," the British author wrote in a message posted on Monday on her Web site.

Rowling noted that while she is pregnant with her third child, she has had the time "needed to tinker with the manuscript to my satisfaction and I am as happy as I have ever been with the end result".