But there's still a lot of work for a lot of people to do before it hits the shops!
Here's a run-down of what has to happen for the book to get into our hands.
But remember: the publishers will be printing masses of first edition copies. So they probably won't be rare and expensive, like first editions of Philosopher's Stone.
- Now the manuscript is finished, JK will work with an editor to make sure it all makes sense and to spot and take out factual errors.
- The cover artist works with her and the editor to design and draw the cover and any other illustrations. The cover should be made early on, so it can be used for advertising as soon as possible.
- Copy editors start working on the manuscript to take out spelling mistakes. This whole process will take a couple of months.
- Once all this is done (probably by about March), the manuscript will be sent to the typesetters, who will make a proof, which is like a rough copy. With 255,000 words, this could take a couple of weeks.
- The editors and copy editors will then read this proof very carefully and remove any mistakes.
- If necessary, it will go back to the typesetters for more changes to be made, and these proofs will be checked until the final version is flawless. JK will also check the book at each stage. This part of the process will also take a couple of months.
- When everything's ready, the final version of the book will go to the printers, along with any pictures, and will be scanned into a computer.
- The printing presses will then roll off hundreds of thousands of copies, which all need to be ready well before the publication date.
- The cover will be glued onto the pages, which holds the book together.
- Finally, the finished books will be sent in good time to the bookshops, so they're ready for you on 21 June!