After Reading "Do Androids Dream of Electric Sheep", I must admit that I was concerned that I would not be able to top that. Fortunately, Ubik surpassed all my expectations. Other reviewers here have detailed the plot, which I think is unfair, since Ubik is a constant page-turner and fascinator. So I will not give anything away.
Fortunately, Minority Report touches upon many of the major themes within Ubik, espcially the industry grown out of Pre-cognition and Psionic ability. It is therefore timely to read this now, and hopefully this will spur on others to take an interest in this most fascinating of authors.
Ubik touches upon many of Dick's core themes (a true Auteur): psychic ability (and its power), faith and religion, regression and postmodernity, death, insanity, drugs, experience etc. etc. However, it truly excels as a narrative, and I completely disagree with those critics who merely saw the characters within this book.
Some points within in are beyond imagination, and will simply blow your mind. The vertigo within this surpasses any other SF I have read. Added to this is some excellent characterisation and social commentary (for example, Runciter vs. Joe Chip, both attempting to save the company, but both representing the dichotomies within capitalism), and some crazy philosophy.
Anyway, before I drool too much, and contemplate starting it again, I shall leave you with my strongest urges to read this book! Forget the rubbish about "well, its not technologically accurate", because that is to lose the point with Dick; unlike other SF writes (most notably Asimov, who likes to portray a history of the future), Dick merely expresses possible worlds (very dark and crazy worlds). Yes, themes do exist, such as 'papes and hovercars and vidphones, but ignore this and concetrate on Dick's stiringly accurate imagination. Sit back and realise that the future is now, in the most unbelievable way imaginable.