At 1074 pages, Under the Dome is not for the fainthearted. The premise is right on the cover. The small Maine town of Chester's Mill becomes suddenly surrounded by some sort of force field that will allow nothing in or out. And when I say suddenly, I mean suddenly. A small aircraft flying over town crashes into it, a beaver gets chopped in half as it walks along, a woman loses her hand as she reaches to the edge of her garden, which lays just over the town line.The reasons for the dome, it's mechanics and the ultimate removal of the dome don't really much matter, although King goes to a lot of effort to make it as realistic as possible. For example, the air starts to go bad within a few days and the dome, although completely invisible at the start, gets covered in the inside with soot and gunk. King uses it to set up an experimental laboratory to see how people will react to being cut off and completely on their own. It's basically the same plot as the TV show, Lost without the exotic location. Although to someone living in Southwest Texas, Maine is pretty exotic.
The story is about how people behave. As you might expect, some behave badly, some behave very badly. Some are heroes, some do what they have to do to survive. Horrible things happen, some good things happen. It is an engrossing story and kept me interested all the time. It's probably a bit longer than it needs to be (does any book really need to be 1,074 pages long?) but it never drags.