Philip K Dick & Ray Nelson 
Ganymede Takeover 

Earth has been invaded — but one human terrorist has discovered a weapon which might change the course of the war!Earth has been taken over by the Ganymedians, a race of telepathic worm-like aliens whose instinct for survival has overridden any human attempt to resist their rule. But there is one man who may have discovered a way to defeat them. Dr Balkani has created a machine which distorts reality, and therefore will allow a determined human to avoid the Ganymedians’ telepathic oversight.But there is one problem — Balkani is a worm-kisser, a servant of the invaders, and may not allow his invention to be used against them…