It might depend on what the nerd likes! The early King, Carrie and Firestarter, are stripped-down (back when he couldn't count on anyone reading a 1000-page book of his!) -- Carrie is half epistolary, heedless of style in the rush to get the story out, whereas Firestarter is a bit more coherent, and has a bunch of parts that stuck with me, including a bloodstain like a comma that is one of the most vivid images I've ever read. The short stories are also often tight and vicious, again especially the 80s ones like those in Night Shift. It is my favorite -- King writes amazing kids -- but it is 1000 pages and may not be the best intro. I also have a great fondness for The Tommyknockers, which is (like Firestarter) horror sf -- but it's also long, and King says he doesn't remember writing it because he was so blitzed on cocaine and alcohol. Gerald's Game and Dolores Claiborne have elements of the fantastic, but are mostly about women's struggles against oppressive and abusive men, with intense characterization and catharsis.

There's a more extended discussion of his body of work in the comments here (http://rivkat.livejournal.com/161301.html) that might provide some advice.