Ubik - a novel by Philip K. Dick. This is typical of Dick's middle and later work, where reality gets a little (or a lot) frayed around the edges. Since I read my copy a long time ago, for a decent plot summary I'm quoting excerpts from a review from Analog (October 1969)]:

"…Like Van Vogt, he has adopted the pattern of extreme wheels-within-wheels plot complexity, in which nobody knows from page to page what is going on and who is on whose side. He usually resolves the tangle better than Van Vogt does…

In the beginning, we have a future industrial espionage yarn unfolding nicely but conventionally. Telepaths and other psi-talented people have an obvious value when it comes to reading trade secrets from people's minds, seeing through solid walls, and so on. Runciter Associates is a kind of counter-espionage organization whose employees can neutralize the psi fields of the spies. Several of the country's top telepaths have vanished, and Runciter is determined to find them. He thinks he has, when a team is hired for a neutralizing job on the Moon. They go there - and are killed. But the story is just beginning.

You have to read this yourself to untangle it, and I'm not sure you will then. I'm not at all sure I have. At first sight, Runciter was killed and the team members are under some sort of attack that destroys them one by one. But things happen that suggest they are dead or in some sort of fantastic limbo, where a live Runciter is trying to reach and rescue them. Time keeps shifting strangely and unpredictably. And there is the patent-medicine called "Ubik," which seems to arrest the change but changes itself…" [P. Schuyler Miller]