The boy wanders up the hill to the town's historic graveyard, where its denizens dub him "Nobody Owens" and vow to protect and care for him. Bod spends the years that follow growing up in the graveyard, educated and cared for by his adoptive ghost-parents Master and Mistress Owens, his mysterious, formidable guardian Silas, and a host of tutors, friends, and all-around quirky characters. As he gets older, Bod begins to learn the truth about where he came from, why he lives in the graveyard, and the danger that lurks beyond the graveyard fence as a result.
I haven't read Coraline yet, but I saw the movie, and I'd say it's about on the same level in terms of darkness / storytelling / age level. Like I said, not what you'd call a dense read; it took me about a day & a half.