Harlan Ellison is one of the most polarizing figures in current literature, having a great many rabid fans, for and against. This is in part due to the only somewhat adopted persona presented in his writing and personal appearances - arrogant, abrasive, overbearing, personal, and volatile. But also amazingly well read, brilliant, fearless in what he undertakes (fearless in topic, in presentation, in his stylistic undertakings at least), and actually morally consistent. When he's good, he's quite good. He is also an acquired taste which some people find far too off putting to tolerate.
His works, while popular, are perhaps more influential than well known in part because he works most prolifically with short stories. Some of his fame (infamy?) comes about because of his introductory essays in his short story collections. Some of his fame or infamy comes because he seems to wander around picking fights, for example his decades-long insistence that his work is "speculative fiction", intended to pose questions about society, and perhaps even be a form of activism, using fiction as the vehicle. The "science" part is a device, a McGuffin. So his point of view is more JohnathanSwift?, than IsaacAsimov.
One of his most famous and infamous projects was editing the Dangerous Visions collections, consisting of two volumes thus far: DangerousVisions?, and AgainDangerousVisions?. This project is typical.
In his willingness to try almost anything, he has written fiction in bookstore windows, written any number of collaborations, created a universe to house stories by multiple authors, edited this, that, and the other, written arguably the most famous season-one Star Trek episode, wrote a novel loosely based on the life of Elvis Presley, run with teen age gangs in New York City, spent a night in jail, marched for civil rights in Alabama in the 1960s, and wrote stories that were the basis of one of the most controversial films of it's time "A Boy And His Dog". Having concluded that the Terminator movie was based on one of his short stories, he sued them and won. One of his short stories, Croatoan, managed to anger both abortion rights feminists and right to life activists at the same time.
In an absolutely typical HarlanEllison episode, when "A Boy And His Dog" was shown on the University of Rochester campus in 1978, it created an uproar. Ellison flew himself to Rochester to debate the women's caucus there. The debate was still famous when I arrived on campus a year later.
Some of Ellison's less Ellison-like works are perhaps his best, such as the already mentioned novel loosely based on the life of Elvis, SpiderKiss?, and a collection of his essays, titled SleeplessNightsOnTheProcrustianBed?.
The author JerryWeinberg is a friend of mine. Still HarlanEllison and UrsulaKLeGuin are the only authors I have considered sending fan letters. Ellison is the only one for whom a letter was written. It exists in draft, never sent. -- JamesBullock
Harlan Ellison and IsaacAsimov were best friends, by the way.--ApoorvaMuralidhara