Dune never struck me as being a particularly sciency book. Maybe this should be moved to general discussion, where it may get more attention...
Ok... my take:
Some time in the future, there is a war called the Butlerian Jihad, of man against intelligent machines. Man won. The new order of the universe is based on navigators who use a drug called melange to find their way around hyperspace. Melange is found in only one place - Dune, and cannot be reproduced.
The political system of the galaxy is split up into various families. The ruling family seeks to play off the other two houses, the harkoneans and atreides off against each other to maintain it's hold on power.
Other group exist, including the bene gesserits, a group of women who conduct breeding experiments in the hope of producing a messiah. Paul - the main character is the product of the experiment.
Basically, the book is about paul's exploits when the harkoneans carry off a takeover of dune when the emperor grants the atreides management of the spice-harvests of dune. Eventually he realises his birthright - including ability to see the future, and pulls off a revolution that makes him the new emperor.