"It is impossible to manufacture or imitate love. No, this will simply cause a powerful infatuation or obsession. It is probably the most dangerous and powerful potion in this room. Oh yes!”, he said nodding gravely at Malfoy and Nott both of whom were smirking skeptically. “When you have seen as much of life as I have, you will not underestimate the power of obsessive love.”

Harry Potter and the Half-Blood Prince

Bloomsbury Publishing
Read by Stephen Fry
Unabridged CD Edition, 2005

JK Rowling

This is the sixth novel in the Harry Potter series and it consists of three main storylines involving Severus Snape and Draco Malfoy - Harry Potter's least favourite teacher and fellow student at Hogwarts, Horace Slughorn - a dapper professor returning to Hogwarts and Lord Voldemort, whose past existence as Tom Riddle is explored in some detail.

It is curious that whilst this novel ties in well with the rest of the series, the various storylines in this novel touch only at various points. The novel lacks an overall theme but the question of Snape's true allegiance is the most convincing candidate.

The most interesting storyline however is that of Horace Slughorn - an acquaintance of Professor Dumbledore. Slughorn is a rather grand figure who's sumptious existence has been turned upside down by the return of the Dark Lord.

A very social creature, he is nonetheless somewhat self-centred and has developed a justified paranoia: he is obsessively concerned for his own safety. But his paranoia produces behaviour more bizarre than the more utilitarian "constant vigilance" of Mad-Eye Moody, who, like Slughorn, has some cause to fear every knock at the door.

It is with reluctance that Slughorn joins the staff at Hogwarts - and in seeking him out, Dumbledore is not averse to using Harry Potter to achieve the desired outcome.

Once at Hogwarts Slughorn relaxes and flourishes and is an impressive teacher. But Slughorn is a man with a deeply troubling past and is a haunted man. Haunted by his own memories.

And it is at Hogwarts that the reason for Slughorn's constant fear finally becomes evident: a past as troubling for Slughorn as surely it must be for the many professors who tutored, nurtured and encouraged Tom Riddle, considering him a model student.

The novel explores in some detail the history of the young Voldemort and this - in spite of the fragmented nature of these explorations - is one of the more successful features of the novel.

The novel also encompasses several romantic attachments between some of the students and whilst this provides some relief from the darker themes, the romances are in the main superficial and make for uncaptivating reading.

The most interesting relationship in the novel is that between Potter and Dumbledore. After some shaky ground in Harry Potter and the Order of the Phoenix, the relationship here gains in intensity and in trust.

But when the two achieve their greatest intensity it is not in a meeting of minds, but in Dumbledore's fierce attempt to persuade Harry that in spite of all that has passed, he - Potter - has a free will and doesn't have to accept unquestioningly every word of the prophecy. And equally in an impassioned and increasingly desperate attempt by Harry to convince his mentor that trusting Professor Snape is a mistake.

The novel reiterates the theme of the power of love and brings fresh emphasis on the value to Harry of his mother's sacrifice. But in spite of some pretty good passages, it fails to maintain the suspense and mystery found in previous books and one of the most interesting characters in the series, Severus Snape, appears less complex and less enigmatic by the end of the story, and the story suffers greatly because of this.