The Three Stigmata of Palmer Eldritch by Philip K Dick
In the overcrowded world and cramped space colonies of the late 21st
century, tedium can be endured through the use of the drug Can-D, which
enables the user to inhabit a shared illusory world. When industrialist
Palmer Eldritch returns from an interstellar trip, he brings with him a new
drug, Chew-Z, which is far more potent than Can-D, but threatens to
plunge the world into a permanent state of drugged illusion controlled by
the mysterious Eldritch.