Heinlein
Robert Anson Heinlein, who coined the word "grok," who created the speculative future histories and alternate worlds that have captivated the imaginations of millions of readers, who, with Ayn Rand, laid much of the popular literary foundation for libertarianism, died 16 years ago on May 8, 1988.
I missed the date, as I don't usually mark the "death dates" of people, even those whom I admire. But fortunately Bill Dennis keeps track of the information at his Heinlein Blog. He also links to a good essay by J. Neil Schulman, which describes Heinlein's works as "how-to" manuals.
RAH, RIP.