With RITUAL, the first of a new series whose links are yet to become clear, Hayder firmly cements her reputation as Britain's finest contemporary crime writer, and certainly the most daring. Fans seem to be split between favouring her two Jack Caffery novels (of which this is a slight continuation), and her two excellent standalones, so given that RITUAL is a kind of blend of both, I'm curious about what the overall reception has been or will be.

After reports of a body being sighted, police diver "Flea" Marley uncovers a severed human hand from the bottom of Bristol docks. Searches turn up no body. But, the following day a second hand is uncovered, previously buried beneath the entrance to a restaurant and now fallen into a drain. Investigations suggest that the person from whom they came, was alive at the time of removal. This is all disturbing enough, but for reports of a small priapic black man hanging around the restaurant and diving silkily into the waters. And there's fear around.

Newly seconded to the Major Crime Investigation Unit of the City, DI Jack Caffery is charged with looking into the discovery. Fresh from his disastrous personal life in London, Jack is still haunted by the disappearance of his brother Ewan when both were children. It's a ghost that leads him to seek out, when free from the case, the Walking Man, an ex-prisoner charged with a horrific crime of vengeance who now spends his days walking the roads of the nearby countryside, sleeping in the shelter of verges and in fields, with only his few possessions and thoughts for company. Jack seems to hope this man will give him some insight into his life, into his anger and desire for revenge.

Flea is not without her own troubles. Just as compelling as Jack (and therefore I am not one bit disappointed that Caffery shares the book with such a fellow rounded, fascinating character), Flea is a bit of a mess, still reeling from her own parents' death in a sinister accident in Africa, for which she shares a great burden of guilt with her brother. She is instinctive, impulsive, dangerously curious, as much driven to investigate the horrific things she suspects might lurk behind the case as she is to investigate the hidden corners of her father's life. And when Jack starts to take her disturbing instincts about the case seriously, the two are set to be mired in a horrific quarter of the Bristol underworld, where human life is cheap and ancient beliefs still hold sway.

And then there's Mossy, a young heroin addict who agrees to do something strange but innocuous in return for a fix, but ends up locked in a cell, with only the presence of a sinister black man called Skinny for company. And soon Mossy will be fighting for his life.

I enjoyed every moment of this. Every last word. There's not been a book I have been looking forward to so much this year, and every moment of anticipation proved worth it. As so often, it's hard to say why you have such incredibly positive reactions to a book, but in my experience it mostly happens when everything about it - the plot, the characters, the back-story, the writing, the setting, the atmosphere etc - just absolutely fits. I adore Hayder's style, her "voice" (though I hate the term), is enchanting, and is so appealing to me that I couldn't put the book down. She has the great suspense writers' way (like Ruth Rendell), of keeping shadows in every corner so you never know what's there, what's lurking, if anything at all. She knows exactly what to hold back and what to reveal, and when to do it. And there's a LOT of material here that needs dealing with, teasing out to us: The present case, Flea's back-story, Flea's current personal life, Jack's back-story, the sinister figures who populate the story, and the mysterious "Walking Man" (who is based on a real-life character and after whom the series is named). And Hayder handles it all with such skill, moving the story at perfect pace.

There are several prominent features to this book. The strength of the characters is one, the strange pull of the back-story is another, and the atmosphere is the third. And possibly the one I relished most. RITUAL is a sinister, unnerving book. It's a strange comparison I'm about to make, but Hayder's skill with quirky fits of the imagination is similar to Fred Vargas. The nature of the quirks is different (Vargas' are lighter, more off the wall, and Hayder's are more imbued with darkness and menace), but the similarity in style is still there, and it's why the books are so intriguing, because the atmosphere is so unusual and compelling. Imagination is the key, the key to making the reader either shiver or think "whoa, that's something new", and Hayder's is sharper than most other writers'. Hints at the supernatural, too, help make things constantly fresh and hidden from the reader, and maintain the sinister, disturbing cast of the plot.

Marley and Caffery are brilliant, Flea in particular. Caffery we know from before (and if anyone is unsatisfied that Hayder doesn't touch on his issues re: Ewan too much, please do bear in mind that this is a series of five books and there's quite a way still to go!!), but Flea is entirely new, and, though damaged, it's a pleasure to be shown her. She really is just as compelling, complex and realised as Caffery, and I'm sure could carry a book of her own.

RITUAL is a complete triumph. Certainly the best British crime novel I've read so far this year. We are treated to some nice twists and turns, and one masterly piece of misdirection by the time the book reaches its satisfying end. I recommend it completely, as much as I recommend all her previous work. Her talent really is quite special.