Ubik is a Philip K Dick book with telepaths and regression through time and messages from elsewhere. The interesting conceit in this one is the notion of half-life, where recently deceased are put in mortuaries where they can communicate with the living they left behind. It’s taxing so it causes the half alive person to decay. In this one it’s unclear to the protagonist whether he is in half-life or if someone is presumptively going back in time to change the present and is causing him and the rest of his group to come unstuck in time, living in someone else’s mind.
It feels more like a horror movie than other Dick books I’ve read and I’m kind of amazed it hasn’t been turned into a movie. PKD books tend to be used that way and this would make more sense (or been easier to do) than A Scanner Darkly