Phillip K Dick 1928 - 1982
Phillip K Dick was one of the most influential science fiction writers of the twentieth century. His works rank as equals to Asimov, Clark and Harrison and have influenced western society just as much and have effected millions more through the movies they spawned.
Some of his more famous works were re-titled for the big screen and Hollywood, for example his 1968 Novel 'Do Androids Dream of Electric Sheep' was renamed 'Blade Runner'. Certainly the title is more catchy and likely to bring in the film goers, but it does perhaps hide the original title question.
The 'Adjustment Team' was reproduced on the screen as the 'Adjustment Bureau' with Matt Damon. Both have merits in their own mediums. These two are just samples, but Minority Report, Total Recall 1990 & 2012. Many big Hollywood stars like Harrison Ford, Tom Cruise and Matt Damon have benefited from the brilliant authors stories.
Throughout his works you can feel his connection to religion a subject that came to dominate his life after a period of illness that combined with medication and experiences at that time. IN many ways you can attribute so much of his work to his religious experiences. And in that there is no doubt it had a positive effect on his writing and influence on the world around him.
Even though the public still mostly think of Asimov and Clarke due to the Robot and 2001 series. Phillip K Dick has probably influenced and touched on the darker side of our future and challenged us to think more deeply than we have before.
Personally he had a huge influence and without doubt he was one of the most influential writers for over fifty years. But most people in the world today would not even know it.