If this was an ordinary encyclopedia entry, most of it would probably be Olaf Stapledon's biography, with a list of some of his works, and some of the people whom he influenced.
Just for context, he lived in England, has been dead for several decades, and has been referred to by Arthur C. Clarke (author of 2001 : A Space Odyssey and much else) as a major influence on his work. The two world wars, communism, and much else of that era left their mark on him.
Actually though, very few of the people interested in Stapledon are interested in him because of when he lived. If you know him at all, it's probably through and because of what he wrote. He is one of the select group of authors still read fifty years after their death by people other than scholars and students. A list of his work isn't really hard to find, so instead I'm going to talk about a couple of his books. The odd thing is not so much that nobody has really successfully done what he did, but it hasn't even been thoroughly attempted.
One of the easiest of his books to find in libraries and bookstores is 'Last and First Men'. This is a future history of humanity spread over millions of years, indeed more, from his own time to the death of the sun. If this sounds as implausible as the worst science fiction and as dull and plotless as a history book, I can only advise you to read it instead of what you're reading now. Not only does the epic scale of his vision come through and sweep you away, but there is also a more personal element, since his future history is made up of individuals as well as rising and falling civilizations. If you don't read science fiction you've never read anything like it - but if you do you probably haven't either. If you don't like science fiction, he is not a pulp author, he is from the era of H.G. Wells and others, when science fiction was not a seperate genre but was understood and enjoyed by mostly the same audience who enjoyed other fiction. If you're interested in what humanity is and what it might become, he is worth reading and thinking about.
The strength of his work is not the only interesting thing about it. Some of his ideas about communism and evolution and other things are indeed outdated, and seeing where we have really and truly moved past his time can be as interesting as seeing how much of his work has held up, or even grown more relevant.
This is not a complete list of his work, I just include it from memory to create a few more softlinks. If you like Last and First Men, you might also try Star Maker. If you live in the United States like me, you might have a little more trouble finding some of his other works.