Having read the book, I was familiar with the plot, but when the movie ended and the lights came up, I was somewhat disappointed, but I could'nt quite figure out why. It took me a little while, but I finally realized that the key points in the movie were simply "exhibited" with no dramatic tension built around them nor much suspense in how all the elements fit together to build to the climax. Certain scenes were good, but the overall movie was weak.
We all knew the plot of Apollo 13 some years back, but the movie was very entertaining because it did build towards something. I was disappointed in the Harry Potter and the Half Blood Prince exhibited like a presentation of certain events rather than a dramatic story.......