"I contemplate the task with mingled feelings of excitement and dread, because I can't wait to get started, to tell the final part of the story and, at last, to answer all the questions (Will I ever answer all of the questions? Let's aim for most of the questions); and yet it will all be over at last and I can't quite imagine life without Harry," the British author wrote in a recent posting on her Web site.

The sixth installment of Rowling's fantasy series, "Harry Potter and the Half-Blood Prince," came out last summer. It has sold more than 10 million copies in the United States alone.

Total worldwide sales of the Harry Potter books top 300 million.

On her Web site, Rowling said she had been "fine-tuning the fine-tuned plan of seven during the past few weeks." She noted that "reading through the plan is like contemplating the map of an unknown country in which I will soon find myself."

Rowling expects to start on the final book, not yet titled, next month.