Three essays on television: The Glass Teat, The Other Glass Teat and Watching. The first two are full of fire and vinegar as he lambasts the medium, politicians and society. He gives them both barrels. Watching he toned things down and stuck to just critiquing television.
Short story anthologies of some of the weirdest, depressing, funny and downright strange. All of them take you on a wild ride. His titles are say so much. A number of his top awards are for stories in these books. I Have No Mouth and I Must Scream. Paingod and Other Stories, Deathbird Stories, The Beast that Shouted Love at the Heart of the World.
An absolute must have for any Harlan Ellison aficionado. I got mine from the SF book club for a song compared to what is would cost today. The Essential Ellison a 50-year retrospective.
Memos From Purgatory. An autobiographical work telling of him as a young man joining a street gang in New York before writing his first novel. It was turned into a teleplay as the first episode of Alfred Hitchock Presents with a young James Caan playing Harlan in 1960.
Lastly is Strange Wine another anthology of short stories.
This only scratches the surface of all the books of his I've read, and there are so many yet to read.