Philip K. Dick is one of the most influential names in science fiction. If you're unfamiliar with his name, it is unlikely that you are unfamiliar with his work. His stories have been made into major motion pictures like Blade Runner, Total Recall, Screamers, Paycheck, and Minority Report.
Check IMDb for a more extensive list.
I highly recommend that you read him. There are several collections available in print, and since many of his stories are very short, they are ideal for those times you're sitting on a bus or waiting in a doctor's office.