I think Wikipedia did a good job on him:
http://en.wikipedia.org/wiki/Harlan_Ellison
In this particular case, he was hired to write the script for
I, Robot. Asimov loved the script. It bounced around Hollywood for a while, changing directors and other personel, then someone else wrote a new script. At that point, the script was published as a serial in
Asimov's, along with commentary by Ellison and Asimov. At that point, the whole project vanished from my personal radar, only to resurface as...
I, Will Smith.