Can't say I understood all the physics but really enjoyed the book. Now I remember why I have so many James Blish books in my bookcase. Great classic sci fi. ( )

To add to the review below, a quincunx is from the Latin for 'five twelfths'. Anyway, the short novel (or is it a novella?), is a slight expansion of the excellent short story 'Beep', which is in the equally excellent collection Galactic Cluster.

Blish is very adept at utilizing complex physics concepts and exploring their ramifications in story form, like the spindizzy drive from Cities in Flight or in the current case, an instantaneous communication radio using the Dirac equations from quantum mechanics (again) and the phenomenon of DeBroglie interference. The DeBroglie effect is basically a theoretic echo created by an atomic particle that resonates through all of spacetime instantaneously at an identical frequency. Huh? you might say, but if such a theoretical device could be made to actually function, well... that's the stuff that makes science fiction great. Just another example of Mr. Blish doing what he did best. A shame he was an unabashed chain smoker and died in his early 40's of cancer.

The basics of the story is an exploration of the above Dirac communicator and a universe in which cause and effect relationships do not exist and there is no such thing as free will. Or is there? I really can't go into it any deeper without giving away the plot, but as a warning there is almost no 'action'. There are basically four scenes, a 'present' that starts the story, a two part look back at the origins of the Service, and a return to the 'present' which begins the story. The main difference between the short story and the novel is that the longer version has a bit more thought put in to the ending and the ramifications are explored in much more depth. Neither are particularly long. Of course, parts are lifted in whole, but the novel is far more satisfying for the extra Blish-ness put in to it, and it's not just word count padding. Can you tell that he is my favorite scifi author? ( )

The invention of the Dirac Communicator in the late 21st century, which promises instant communication over interstellar distances, is a starting point for a discourse on causality and faster-than-light travel. This is not typical Blish: it is more philosophical speculation than a short novel.

I found immensely enjoyable.

To save you a trip to the dictionary, Quincunx is an arrangement of things by 5 in a rectangle; particularly of trees repeated indefinitely, forming regular groups with rows running in multiple directions. One of the protagonists describes the Dirac Communicator technology as being able to look down on time as if it were a set of trees, and determine which will grow, and which will wither. ( )