"Flow my tears..." is a book that exhibits Dick's (heretofore PKD) usual thematic obsessions in an expert literary way, having been written during the last decade of his life, in between theological treatises and attempts to explain his personal epiphany. It actually reads like he is showing off that he can write good old SF to his publisher who's asked him to clean up his act before an audience that's not interested in religious revelations. The fourth part of the book, telling what happened to the heroes and institutions involved in the far future, is reminiscent of a B movie ending, and probably reflects the author's overindulgence in the commercial nature of this work.
The book is very reminiscent of Ubik, centered on a man's struggle to make sense of his reality that has suddenly changed (to a very unpleasant one), and it could have been written in one - extended - sitting, PKD driving his points home from page 1. It can certainly be read in one sitting, and its frantic pace will compel most people to do so.
As per usual, the environment only serves as a context for PKD to bring his social commentary home. This shouldn't detract, however, from the fact that the particular world, a heavily policed fascist state where universities and their students (presumably standing for free thought) are offenders by default, is one of his most successful predictions, as we can already see it happening. PKD seems to be aware of it as well, for he describes its functions and mechanisms in unusual detail.
That said, the novel is an exploration of human behaviours and emotions, how they interact and which bring which about. Grief and love being prime examples, and indulged in by a series of unlikely characters, the novel also touches on selfishness and selflesness, sexual promiscuity, cruelty and kindness and the deeper meaning of personal success, without neglecting, of course, the usage of copious amounts of hallucinogenic substances.
The novel features a wide and varied range of perplexing characters and accompanying behaviours, deeply explored and perfectly aligned with their environment. It is one of PKD's most sympathetic works towards his heroes, and clearly paves the way for his later book, "A scanner darkly", his peak of empathic prose, and possilby his best.
"Flow, my tears..." is a powerful treatise on how human behaviour shapes to fit its environment. So strong, in fact, that the author doesn't even bother, for the most part, with the 'details' of the world, hence the rating of 4 stars. This novel is for the serious bookreader (not limited to 'SF fan') who will see past the premises and into the substance of the meanderings of a truly brilliant mind.