So much of his work is not in electronic format and out of print- it's sad.
Someone put it better than I could - Goodbye to the most tireless ambassador of the future. He collaborated with one of my favorite authors, Steven Barnes, a lot to great success (Beowulf's Children, The Legacy of Heorot). A bit from him about Pournelle:
Steven Barnes, with whom Pournelle collaborated on several novels, told me in an email that “he was an absolute original, one of the best and smartest men I’ve ever known.”