The fifth Harry Potter book weighs a whole kilogramme and most postal workers will struggle to carry more than a few copies at a time.
So Royal Mail is laying on loads of extra vans to save their staff's muscles working overtime.
Not disappointed
The extra vans and staff should make sure that none of the young (and old!) fans are disappointed, a Royal Mail spokesman said.
But they did warn people to stay at home if they're expecting the book to come through the post.
Stay in
Because the book is so large - it's 768 pages long - it won't fit through most people's letter boxes.
If fans aren't in when it arrives, they'll get a note saying they have to collect it from the Royal Mail sorting office.
You've been warned!
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