I'm reading a lot at the moment, as I get deeper into writing studies. Part of being a good writer does involve a lot of reading. At the moment I average about 1 per week, so I'm not as prolific as your grandmother. I'm not overly fast, just do lots of it.

I will take a look at her stories when I get the chance - thanks for letting me know about them.

Have you read Ursula K Le Guin, Robert Heinlein, Philip K Dick, Richard Morgan, William Gibson, Roger Zelazny, Orson Scott Card, Ray Bradbury, Kurt Vonnegut, Larry Niven, Frank Herbert, Douglas Adams, Arthur C Clarke, Daniel Keyes, Theodore Sturgeon, J G Ballard, Alfred Bester, Gregory Benford, Olaf Stapledon, John Brunner, Richard Matheson, James Blish, Frederik Pohl, George R Stewart, Michael Moorcock, Andy Weir, Joe Haldeman, Hugh Howey.

These are some of the names I can think of in the Science Fiction genre. There are many more, but you'll find some great books amongst these authors.

I don't know your exact tastes, but I can highly recommend Robert Heinlein - Stranger in a Strange Land, and Joe Haldeman - The Forever War.