Obituary writers across the globe must have had a field day when Douglas Adams died. It was a short life, but he packed a hell of a lot of action into his forty-nine years.
The Hitchhiker's Guide to the Galaxy, Adams's most famous work, began as a radio show in 1978. The Hitchhiker series eventually included five full-length novels and the short story Young Zaphod Plays it Safe. The books describe the adventures of an unremarkable Englishman named Arthur Dent, who, after Earth is destroyed to make way for a hyperspace bypass, ends up tagging along on his alien buddy Ford Prefect's travels through the universe. Adams wrote two other novels, Dirk Gently's Holistic Detective Agency and The Long Dark Tea Time of the Soul, and was the co-creator of an environmentalist book and CD-Rom set called Last Chance to See. The Salmon of Doubt, a collection of Adams's miscellaneous writings, was posthumously released in 2001.
Availability: Libraries. They're available for sale everywhere, and mostly in paperback. Check used bookstores, too.