Arthur C Clarke was a giant of Science Fiction. The first book of his that I read was "Islands in the Sky", followed rapidly by his earlier works. This was back in the mid-'50's. One of my favorites is (and will remain) "A Fall of Moondust", even though the theories proposed there have been proven wrong.
Arthur clarke is the person who first proposed geosynchronous orbits. He will be missed by everyone who had that touch of wonder that was instilled by his work.