Before I read PKD or Gibson or Ellis or Stephenson or any weird-ass author I can refer to as my favorite, there was William Sleator. I remember obtaining the first novel of his I read -- Interstellar Pig -- through one of those order-by-mail school book clubs. After that, I exhausted my local library's surprisingly well-stocked collection of his novels. Well, not that surprisingly; two of the librarians (the ones I would go there to hang out with) were pretty big on SF.
His novels were really unlike most young adult SF I'd read until that point. They were brutal: things changed for the young men and women involved, and they didn't always change for the best. People fought, people died, entire lives were altered by the choices of kids not who weren't too different from me. Endings weren't necessarily happy, and a moral ambiguity penetrated every action. In his 1974 Baby's-First-Kafka novel House of Stairs, a group of children were practically tortured with no savior in sight, left to suffer or escape by their own device. There was an independence to his novels that no other author could capture for me. For better or worse, nothing could stop a Sleator protagonist except themselves.
William Sleator died two days ago, at 66. But his books will live on and hopefully inspire more kids toward science and independence.