It is normally bad form to assume that the reader of a review is familiar with the subject matter. However unless you have spent the past six months living under a rock with cheese in your ears you will probably have at least passing familiarity with the world of Harry Potter. If you don't . well . this is the sixth book in the series, and it would be pointless to read it without reading the other five books first.

The wizarding world is at war. This pleasing alliteration sums up the state of affairs at the start of Harry Potter and the Half Blood Prince. The opening chapter shows us the opening salvoes of this war through the eyes of the Muggle Prime Minister. Death, destruction, and despair (due to Dementors) are rife in the land, and neither Wizard nor Muggle is safe. The plot thickens rapidly. We find that Snape may be closer to the Dark Lord than we ever thought, and we learn that Draco has been given a mission by Voldemort himself. The opening of the book creates a real and effective sense of mounting danger.

Unfortunately, the pace is not maintained. The war with Voldemort, who finally revealed himself at the end of the fifth book, fades quickly into the background, taking a bizarre second place to Quidditch practice and potions lessons. Indeed, even the eponymous plotline - the mystery of the Half Blood Prince - relates more to Harry's schoolwork than to the schemes of Lord Voldemort. There are occasional references in the Daily Prophet to the off-page deaths of one or another member of the Potterverse's vast supporting cast. These events, however, always seem strangely distant.

Much of the book is taken up with elaboration on the back-story of Lord Voldemort. The revelations are sometimes obvious (he had an unhappy childhood, and was cruel and arrogant), sometimes genuinely interesting (ever wondered what the deal was with the diary in Chamber of Secrets ?), and sometimes completely random (details withheld to avoid spoilers). While this is moderately interesting, it is rather dragged out, and the prevalence of Voldemort's past serves to highlight the absence of Voldemort's immediate influence.

The book, much like Order of the Phoenix and Goblet of Fire suffers from a surplus of plotlines and a shortage of plot. There's the teenage romance plotline, the Draco plotline, the Half Blood Prince plotline, the Quidditch plotline, the Voldemort's-history plotline all vying for space on the 607 pages of the book. There is, however, very little actually driving the action. Of the disparate plotlines, Draco's is by far the best. Young Malfoy becomes almost sympathetic, as he discovers what it really means to serve the Dark Lord.

It is my custom to conclude reviews with "so should you read this book" - that question is probably moot in this case. If you have read books 1-5, you're probably going to read book 6 (if you haven't already). If you haven't read books 1-5, then chances are you lost the thread of this review two lines in.