I started watching Under the Dome on tv when it came out and wasn't overly impressed. Somebody on Twitter (I think) said the book was better so I got it out of the library.
It's big. It's really, really big. In the acknowledgements, King thanks someone for trimming it down from the oversized monster it started out as. This 'trimming' took the book down to roughly a thousand pages, so I shudder to think what it started out as.
I finished it last night, with my husband sleeping beside me on one pillow instead of his customary two, because I had to borrow one to prop up the book.
Overall? I kind of liked it. It was better than Duma Key. Not as good as 11/22/63. It did some of the things King does well, sketching characters quickly but well, giving you short, sharp glimpses into their lives, painting an ensemble cast and then setting them loose to interact with each other. The group of kids was fun and endearing, reminiscent of the children in It, who cemented King in my mind as someone who writes children very well. There are some scenes that are extremely striking and moving. The plot as a thought experiment was interesting, and the end was logical enough, although it felt a little perfunctory. As an 'extreme logical conclusion' of small-town dynamics, it was credible. I felt sort of outraged on King's behalf by what had been done to some of the characters by the tv show.
Was it overwritten? My first impression is to say yes, absolutely, but by the end I also kind of felt like the experience of reading the book mirrored the experience of the people caught inside the dome - it's entirely possible that this was accidental, though. I don't feel like it was a waste of time reading it, although I'm not entirely sure it would have been a mistake to give it a miss either. I have higher hopes for Joyland and Doctor Sleep, both of which are on my pile.