The book you've described is a UK first edition of "Harry Potter and the Half-Blood Prince" by J.K. Rowling, published by Bloomsbury in 2005. What makes this particular edition rare and interesting is the misprint on page 99, where it states "eleven 'outstanding' O.W.L.s" instead of the correct "Ten Outstanding O.W.L.s." This type of printing error can make a book more valuable to collectors.
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