I find it inconceivable to describe the content of the story, or even to make a simple summary, the risk of revealing an important part of this exciting and futuristic story written in nineteen sixty-nine and supposed to take place in the years ninety, while we are in the year two thousand!
For translation, is not bilingual myself, if I redo most critics, it seems well made. Anyway, I have, at no time toiled in understanding the novel, despite its complexity; I think, above all, the various back in time (30 years), who themselves are frequent in the story, since primordial!
It was a great moment of reading, but not only because Ubik transported me in my dreams. For this ability then I like this author; beyond the imagination of PK Dick, his pen, his talent to create a good plot, its credibility in a science fiction story, it causes you and pushes you to reflection, while remaining accessible to the reading by multiple games in the space-time.
So here, in my opinion, Ubik is "the" pure SF book, having read the first hundred Perry Rhodan (fairly close to a part of the history of Ubik) or the excellent Entremonde Neil Gaiman ( particularly for its opulent appearance dealing with space-time), I remain convinced that PK Dick was one of the best writers of science fiction!