The thing I like best about Semiosis is the structure. Browsing through the reviews on Goodreads, it seems to have ticked no few readers off that the book spans over a hundred years and jumps sequentially from character to character through the generations. But I love it. I think there are some stories that simply can't be told in the standard one-hero narrative of most adventure books, and the story of the planting and nurturing of a human colony on another planet would suffer if a writer tried to cram it into that format to please the publishing industry.
Another thing I really loved was the way Burke has her characters assign Earth labels to organisms that are very very obviously not at all similar to their namesakes on Earth. On Pax, 'cactus' are plant-like organisms that float because they don't have roots and have sacs full of hydrogen gas, eagles are bipedal, fire-making predators, and orange trees have long thorns, aerial roots, and are capable of duplicity. Not only does this conceit make Burk's prose much less bulky, but it creates a continual sense of discovery, tension and exploration as the scene that you feel like you can almost imagine is suddenly revealed to be something else entirely.
Burke's attention to detail also shows in the delightfully subtle way she shows the growth of human culture on Pax, from the first generation of Earthlings through the development of traditions, belief systems, taboos, and social classes. She has a light hand and uses exact, vivid details in an economical way that doesn't distract from the extinction-level event(s) unfolding around her characters.
That's only a few of the very cool aspects of SEMIOSIS--by the time I was halfway through, I was already recommending it to people, and now that I've finished it I have book two on hold at the library!