Combining the atmosphere of Celtic folklore with a plot reminiscent of Shakespeare's "Hamlet", as well as an intricate plot (including a huge twist halfway through that will completely turn your perception of the story on its head) and likeable characters, "Power of Three" is one of Diana Wynne Jones's best novels - and so inevitably it is one of her least known.
Set on moorlands inhabited by Giants, reptilian Dorig and tribes of warrior-like clans, the first two chapters introduces the rest of the story to come. First, Adara and her bullish brother Orban come across a young Dorig princeling, and Orban demands the beautiful collar around its neck. Refusing, the Dorig places a deep curse upon the collar that will bestow bad luck upon the holder and the surroundings.
Chapter two takes place several years later when Adara elopes with the chief of a neighbouring Mound. This reads like a Celtic legend as the hero Gest must perform three impossible tasks concerning riddles, collars, standing stones, Dorig and Giants, and exactly how he manages to accomplish these feats is a mystery that (like the influence of the curse) is explored more deeply in the rest of the book that skips onto the next generation.
Gest and Adara's three children are Ayna, Gair and Ceri. Ayna the eldest can answer any question posed toward her, whilst Ceri can not only find anything that is lost but manipulate matter with his mind. Gair however is devastatingly normal, and so considers himself a disappointment to his entire community. But with the evil of the curse winding its way into all aspects of life (including food supply, war with the Dorig, and an unwelcome invasion of relatives into their Mound), Gair finally reaches breaking point and heads for the countryside. Tailed by Ayna and Ceri, the three siblings find adventures with both Dorig and Giants waiting for them, and realisation that the Moor itself is in danger of destruction.
In terms of theme and plot, "Power of Three" may very well be the deepest and most complicated novel for young readers that DWJ has written. Exploring the definition of humanity, the worth of the individual and the necessity for peace at its core, the book also has plenty of humour, quirky characters and intricate subplots - far too many to properly explain in a simple review. But it is worth saying that this book in particular has a range of interesting and vivid characters - from saintly Adara, woebegone Gerald, bossy Brenda, spoilt Ceri, sage-like Ayna and the odious Ondo. But the spotlight mostly falls on Gair, and he is a protagonist that most will find very easy to relate to - melancholy and serious, but determined and intelligent, and altogether a likeable guy.
The author also makes some wonderful connections between characters - the siblings in particular are warm and affectionate (most of the time) and the friendships that Gair forges within the story are also realistic and enjoyable to read. But then again, DWJ is an expert at portraying human behaviour and it should come as no surprise to any familiar readers that such things are handled just as well here.
"Power of Three" definitely has my recommendation, though I should warn you about reading other reviews on the story, as some of them give away the big twist - something that shouldn't be revealed if you want to truly revel in DWJ's genius.