Boneland, By Alan Garner

After 50 years, a unique trilogy of novels finally reaches its mind- expanding final

Things have not gone well for Colin and Susan since they set about seeing off encroaching forces of evil, first in Alan Garner's The Weirdstone of Brisingamen (1960) and then The Moon of Gomrath (1963). Nearly 50 years later – surely the longest time ever taken to complete a trilogy? – they turn up again in Boneland. Or at least Colin does, now a wild-haired, mad Professor of Astronomy. Susan, always more in touch with hidden powers, has long been taken by the Pleiades into another world when a sacrifice was needed to save the normal order of the universe. Colin, bereft, can only sense her and occasionally catch the odd word snatched from the ether or communicated during a dream.

It's a fairly preposterous plot, then, not made any simpler by the existence of a parallel story involving a prehistoric shaman known as the Watcher, also charged with having to preserve the world from destruction. Yet it never does to underestimate Garner, a writer with the ability to make familiar words sing off the page as if part of a new poetic language. Each new book is an adventure into previously uncharted territories.

Too much sustained fine writing can also feel remorseless. Garner knows this, but whenever he goes into less exalted mode, Boneland becomes unstuck. In need of treatment away from his recurrent visions, Colin seeks the help of Meg, described as a psychiatrist but coming over as someone more in the Rolf Harris school of relentless facetiousness. Colin's Asperger-type lecturettes to her on quantum physics, time, maths and anything else he can make suitably abstruse also become trying.

Young readers warmed to Garner's 1967 masterpiece The Owl Service because they could sense the urgency of the story, whatever its ambiguities. Boneland however is not in any sense a children's book. A weeping middle-aged man who wears a green silk hood is a far cry from fresh young Colin. But then, describing what sort of adults child characters have grown into is always tricky – who could forgive RM Ballantyne for turning the charming young adventurers of The Coral Island into the cold-hearted moustachioed killers of The Gorilla Hunters?

Even so, at 149 pages, this novel packs in an enormous amount and invites re-reading. Set in the Cheshire hills around Alderley Edge, where the author has always lived, it has as its real heroes the rocky landscapes that have their own stories to tell. They have found their ideal interpreter. Garner ranges through history, endowing each cleft and protuberance with its own role in a cosmic struggle between light and dark.

True, the story that emerges is often obscure and over-the-top. But if it is the manner of their telling that ultimately proves to have the greatest worth for their audiences, then this novel should live on after more conventional fare has long fallen by the wayside.