If this novel, a return to the beloved and frightening Alderley Edge of his earliest writing, disappoints, it is because Alan Garner conjured something so beautiful and unsettling in the past using these same dark materials.

This reader, at least, wished for him to weave that spell again. Garner's keen sense of the believable supernatural makes him such an unusual and powerful writer. So perhaps he should know that sometimes incantations fail, especially if they are growing old. The right words are uttered in the right places, but there is no revelation: all the chalk circles, sacred rocks and holy pools remain as they are – chalk, rock and water.

In Boneland, Garner writes what he once said he would not write: the final part of the trilogy begun with his first book, The Weirdstone Of Brisingamen (1960) and continued in The Moon Of Gomrath (1963). In these thrilling, sometimes baffling adventures in modern-day Cheshire, young Colin and his sister Susan are thrown into an eldritch world of Old Magic, High Magic, wild hunts, demonic witches, sleeping knights, dark elves and terrifying curses.

Garner says he does not intentionally write for young adults, and Boneland is certainly not aimed at that niche. This is not the domestic magic of JK Rowling's spell books, the convenient hocus pocus of Hollywood or even Tolkien's more mystical forces. This magic is dangerous, it churns like lava under the mantle of ordinary life. Garner's contemporary settings are thin shifts that lie over a turbulent, older world, which is constantly threatening to rip the seams of our modern, secular, mechanised society. Humanity is not big enough to control or even remotely understand these extra sensory powers, and indeed can be sent mad, rendered brain-dead or destroyed if thrown into its storms. As in his beautiful (indeed, almost perfect) third book Elidor, a smashed church window can be a portal to another time, and urban ruins become transfigured landscapes, but shorn of comfort or explanation.

So in Boneland, the modern-day tale is told in tandem with a primeval and confoundingly opaque narrative that may reward, I hope, repeated re-readings. There, in some distant past, a shaman works his tools in caves and crevices. But in the modern day, we see Colin as an adult. He is now a genius with interesting mental tics and a scar on his neck, and works at the Jodrell Bank Observatory array, also in Cheshire. He has no memories of his life before he was 13, and is haunted by the loss of his sister. He seems to be looking for Susan in the stars. He lives in a hut in a quarry and although he has an amazing mind, is a tortured and frightened soul. So he begins consultations with Meg, a shrink who unlocks his mind and, in doing so, unlocks much else beside.

The modern day narrative, in comparison to the lyrical but frustrating Bronze Age (or Stone Age, or indeed, it may be extraterrestrial) story, is sometimes awkward, and its dialogue often clanks into place like the gears of Jodrell Bank's own venerable 1950s Lovell Telescope. Meg, in particular, has some ripe lines that induce winces. There is also a narrative rug pulled from under the reader at the novel's conclusion that can be seen twitching well before Garner would wish.

The climax, following this flawed journey is, unfortunately, an unsatisfying one, although one's affection for Colin and his ineffable plight, and that of poor Susan, grows strong. In that sense, it is a deeply sad book. Garner is also, as he has always been, a master of the unnerving domestic detail, and can conjure a sense of place, a sense of mythic heft in both landscape and object, which survives here intact. But unlike his best work, which is some of the finest writing, Boneland does not linger, perplex or haunt. One wonders if distraught Colin and lost Susan were literary spirits that should have been left well alone. Sometimes, perhaps, it really is best not to go home again.

Boneland

Alan Garner

Fourth Estate, £16.99