JK Rowling has won loads of children's awards in the past but on Tuesday her latest book won a major adult award.
Harry Potter and the Order of the Phoenix won the WH Smith Adult Literary award, beating Whitbread Book winning author Mark Haddon.
JK said "I am honoured to receive this award, unabashed adult Harry Potter fans are very dear to my heart".
Although it's not the first adult prize she's won, it does show that Potter books aren't just popular with kids.
She's currently writing the sixth Harry Potter book, which, no doubt will be enjoyed by both children and adults alike.
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