http://www.gutenberg.org/ebooks/author/355
My personal favourite so far has been 'Mysticism and Logic and Other Essays' with 'Analysis of Mind' currently at the top of my reading queue. Not everything he did was like reading 'Principia Mathematica' and his writing is very open, readable and eloquent.
* The Problems of Philosophy (1912) gives a short introduction to philosophy that he at the time considered "positive and constructive". https://www.gutenberg.org/files/5827/5827-h/5827-h.htm
* Mysticism and Logic and Other Essays (1901 to 1915) is an anthology of his ideas that were still evolving even then. https://www.gutenberg.org/files/25447/25447-h/25447-h.htm
Durant's writing is great too, but The Story of Philsophy doesn't have the depth of The History of Western Philosophy, and, I actually enjoy Russell's snark along the way.
"Mathematics, rightly viewed, possesses not only truth, but supreme beauty—a beauty cold and austere, like that of sculpture, without appeal to any part of our weaker nature, without the gorgeous trappings of painting or music, yet sublimely pure, and capable of a stern perfection such as only the greatest art can show. The true spirit of delight, the exaltation, the sense of being more than man, which is the touchstone of the highest excellence, is to be found in mathematics as surely as in poetry."
Betrand Russell: "Mysticism and Logic and Other Essays". [http://www.gutenberg.org/etext/25447]