'Soylent Green' author dead
He wasn't one of the most famous SF writers, but he'd been plugging away for more than half a century, including a proto-steampunk novel, A Trans-Atlantic Tunnel, Hurrah!, which took place in a world where the American Revolutionaries lost, the British still rules America, and a descendant of the traitor George Washington is trying to redeem the family name by building the engineering structure of the title. I've never read the book, but it's been on my list for a long time.
Harrison also wrote a series of comic futuristic crime novels about "Slippery Jim" DiGritz, aka "The Stainless Steel Rat," and is probably best known for Make Room! Make Room!, which was the basis for the Charlton Heston SF film Soylent Green. Typical for Hollywood, the film was so loosely based on the novel that the title element itself, the food substance soylent green, does not appear in the book, and it certainly isn't people.
But Harrison had a good sense of humor about it, and recounted his experience with the film in interviews (I believe I read it in John Brosnan's Future Tense: The Cinema of Science Fiction and/or in Omni's Screen Flights: The Future According to Science Fiction Cinema edited by Danny Peary, both, alas, out of print). He said the overpopulated Earth was the point of the novel, not the surface murder mystery, so it didn't really matter.
He also got permission to visit the set, where he handed out copies of his book to all the technicians and crew, pointed out scientific errors (in this petroleum-poor future, they had plastic bags in one scene) and even helped Edward G. Robinson understand his character better ("You're me," Harrison told the great actor, because the author would be thew same age as the character by the time of the film), and the only character in the story who remembers a world where natural food was widely available in great variety, where two families weren't forced to live in one apartment -- y'know, the good old days).
If you want to read a full obituary, The Guardian has one here.