An astonishing trilogy, best read, I suspect, in one big 1,000-plus paged lump as presented here. Helliconia is a formidable work. The timescale is vast, the themes are difficult, the human dramas, though full of intrigue and passion, battles and spectacle, are unashamedly literary in the demands placed on the reader. The trilogy, in fact, expects full intellectual and emotional engagement in order to fully appreciate the scale and complexity of Aldiss' achievement.

Helliconia is a planet with two suns and two years. The shorter years are over four hundred days long. The greater year takes milllenia. At one end of the great year the planet is shrouded in extreme cold, at the other in extreme heat. Civilisations rise and fall over the course of the year, only for the survivors to come forth again in the Spring and start all over again. Helliconia is an epic of climate change.

Vying for supremacy on the planet are two species, the phagor, who dominate in the cold time, and humans who dominate in the warmth. The two are profoundly hostile to each other, and yet fundamentally linked in the struggle to survive. Overhead is a research station from Earth, the Avernus, cataloguing and recording and transmitting its findings home.

Life persists, in abundant forms and varieties, though the processes are cruel and profligate with individuals, but the books chart the stories of individuals as they struggle with their strange world, trying to understand it or shape it or control it, often with plenty of cruelty of their own. Can the cycle be broken? Can memory and civilisation persist, and if so at what price?

The worlbuilding's the thing here. Designed, envisioned and delineated with great care and detail, Helliconia is alive on the page, but though marvelous and splendid and strange, it's more than a simple vehicle for escapist fantasy. It's a world in some ways even more circumscribed than our own, partly because of the strictures of the environment and partly because of humanity itself. It's a big, broad, shambling masterpiece. Every human is flawed, every venture doomed and the vast natural processes designed to preserve life are merciless and inscrutable, yet ultimately Aldiss unifies these elements into a vision of universal empathy in which intelligent life must adapt to to the natural vehicles that keep it alive.