Well I think this text might indeed include some information you might not want to read before reading the book yourself, but those pieces of information are indeed important for a review of this book. So if you haven't read it up to now you might want to leave this review untouched until you have finished reading. After that you are welcomed to comment giving your opinion on the book.

Before reading the book I could find the info that "a main character will die" in the book and various ideas and rumours about who the "Half Blood Prince" might be. My own guess on the latter topic wasn't too bad, though I was shocked with the ending.

Just like the "Order of the Phoenix" I think this might be a book not really suitable for children up to the age of 12. This time not because of heavy fighting scenes and cruelties but for a very complex and complicated story I might think especially children could have problems to follow. So a big part of the story is hopping from one wizard's memory to the next while Dumbledore tries to help Harry understand who Voldemort, sorry, Who-Know-Who, is and what he might be up to. The next big part of the whole story is of course about the "Half Blood Prince" which Harry doesn't find out about until the end of the book where the Prince himself tells him who that is.

While reading I had two burning questions: The first of course being who the Prince was. As the Prince prooved to be really good at Potion making and nasty spells my guess was quite soon that it might be Snape which turned out to be right not later as to the point where Harry defends himself with one of the spells he found in the book against Malfoy. Snape's reaction to what he saw was quite obvious indicating that he knew more than he should know about that spell.
The other question was why Dumbledore must give Harry so much of information about what he knew about Tom Riddle's life. In the end that was clear: He needed to prepare Harry for the case that Malfoy's plan of killing him would succeed. Though in the end it wasn't Malfoy but Snape who killed him rejoining the Death Eaters.

I don't think killing Dumbledore will do the Harry Potter series any good. I think it was a character who gave the stories some magic in some way as you never knew exactly how much Dumbledore really knew about what was going on. I'm curious if the next book will go on with that dark atmosphere and if it's possible to let the stories remain as fantastic and magic as they were with Dumbledore still alive.