Well, I just finished reading Ubik by Philip K. Dick. And, as anyone with any knowledge of Dick knows, it was a trippy novel that plays with reality. And causes the reader to ask questions. "What is reality? How is it constructed? And how can I be certain that it contains beings other than myself?"
These, of course, are not easy questions. But they are, in essence, the questions that Dick's protagonist Joe Chip, an electronics technician working for a company specializing in detecting and eliminating psychic "threats." Which includes things like spying and pre-cognition.
Chip, along with some colleagues, all of whom have legitimate psychic powers save him, are hired to do a job on the moon. However, a terrorist detonates a bomb that kills their company's CEO. And Joe Chip, who takes over, knows who is responsible. But, before he can report this to the proper authorities, members of his team begin showing up dead. And reality seems to "devolve" back in time from Chip's present.
And even after Chip seems to have solved the mystery, we end up scratching our heads again. As another character fishes for some coins...
In Ubik , Dick has created a mystery like no other. A wonderful book that will keep you guessing. And, at the end of the book, you'll scratch your head. And smile. Clever and thought-provoking, I give Ubik the highest recommendation. Even the dated bits -- like having nearly everyone smoke even at the office -- seem to be merely quaint. Which is why Dick reigns supreme among the "classic writers of Science Fiction" in my opinion.