Harry Potter and the Half-Blood Prince

Harry Potter and the Half-Blood Prince was a book in the Harry Potter series, released some time in the 21st century.

A poster advertising the book, depicting Harry Potter and Dumbledore, was hung in Books Unltd on Charing Cross Road. (COMIC: A Groatsworth of Wit)

Behind the scenes
The poster, oddly, seems to depict the cover artwork of the book's North American edition, rather than that of the UK edition.