I see no one jumped in yet to describe Helliconia, one of my all time favorites also.
I would say it a lot more straightforward than Gene Wolfe, with worldbuilding taking center stage over character development or plot. The story spans thousands of years, reflecting the particular dual sun planetary changes from ice age, to lush tropical exuberance in Helliconia Spring, changing to unforgiving desert in Helliconia Summer and returning to cold in Helliconia Winter. Civilisation follows planetary cycles developing in the warmer ages and devolving into mere survival under the onslaught of cold. The science fiction part comes from the bird-eye view offered to the reader and the ready explanations of climatic, social events. There are references to Earth and space travel. The fantasy part comes from the exotic animals, the multiple intelligent species [humans, phagors, anthropoids] and exotic fauna. There's magic of a sort, dealing with ancestor's spirits communicating with the living. Heroes are seen in the wider context of planet wide forces taking the role of fate, trying to conquer or forced to adapt to the environment.
