The three books in Brian Aldiss' Helliconia series are Helliconia Spring, Helliconia Summer and Helliconia Winter.

The planet Helliconia

Helliconia is set on a planet that is rather like Earth in many respects, except for two things. First, Winter lasts for 600 years. For a more detailed account of the Helliconia seasons, see the physics of Helliconia. Second, the planet is inhabited by humans as well as a second species - the Phagors, furry creatures that thrive in the extreme cold of winter and at the polar caps.

The eternal rise and destruction of civilization

The long winters have the effect of ending any achievements and virtually wiping out the human race. The Phagors enslave most of the ones that remain. Only when the next summer comes (in a millennia) will this again be reversed and the Phagors become the slaves of man. An interesting twist is that the mutual enslavement is what enables each species, human and Phagor, to survive the seasons of Winter and Summer respectively.

Helliconia Spring

Helliconia Spring is set during the period when the great winter comes to an end and the planet ‘wakes up’. Humanity is starting to rise from barbarity once again. As the snows recede, humans rediscover skills and knowledge long forgotten and start to regain mastery of the planet.

Helliconia Summer

The second book is set during the great summer. The human race is dominant, civilization is at a pinnacle of mastery of the planet, and the winter is a dimly remembered myth.

Helliconia Winter

Eventually, the cycle moves on, and winter begins to return, destroying all of the human’s greatness, their civilization, and robbing them of hope. The phagors are on the rise. The humans try to resist, to hold on to what they had, but their fate is inevitable. 

In Aldiss at his very best, the themes of the book are no less than the destiny of the human race. The Helliconia series deals with these huge events and ideas by following several characters from all levels of society. The ideas are conveyed through simple, powerful storytelling about ordinary people trying to do the best they can with their situation. While there are numerous characters and plots, they weave and intersect in a variety of ways. The end result is a powerful reading experience.

One cautionary note: the Helliconia series is long and takes some time before the pace picks up. These are not a quick read. However, if you do start them, the effort will be well worth while.