'Under the Dome' Renewed For a Second Season

When Under the Dome premiered, I was presuming a single season that encapsulated the entirety of the Stephen King book it was adapted from. 

But now, with the news that CBS has renewed the series for a second season, now I have to wonder just how far this can be drawn out?  Is the book still encapsulated just in the first season, or was this the plan all along, using a piece of the story for the first season?

I guess it could make sense, to parse out the show originally, and possibly have a wrap-up movie ready to go if the show didn't get renewed.

But this is CBS...  the kind of networks at the moment.

In the renewal announcement, CBS Corp. CEO Les Moonves made mention of the business model this show was built on, praising the relationship they had with Amazon, who aires the episodes four days after they air on CBS.

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