Paprika

Dreams are the windows to the psyche.
What happens when you break the window?
The Institute for Psychiatric Research is at the cutting edge of mental healthcare. Brilliant psychotherapist Atsuko Chiba has pioneered their dream therapy, allowing doctors to view patients' dreams in real time to diagnose disorders hidden in the subconscious.
Atsuko wants to take it further. Using a device that allows her to enter dreams physically, and interact with them, directly treating the patients rather than simply diagnosing. It hasn't been approved for such use, but disguised as the beautiful Paprika, Atsuko has been doing so covertly, on people willing to pay for quick solutions to shameful problems.
When the prototypes of a new, more powerful device disappear from her partner's lab, and it becomes clear that it can be used not just to treat... but to control and harm. And the more it is used, the more the borders between waking and sleeping deteriorate, for everyone.
Atsuko must find who stole the prototype - a jealous rival? An opportunistic newcomer? - before dreams and reality combine and become a nightmare.

With a new, authorised English translation by Helen O'Horan, Yasutaka Tsutsui's mind-bending masterpiece joins the SF Masterworks.