it's a kids' book. you could probably read the whole thing in an hour. the titular little girl finds a door in her house that opens up a surrealistic one-off version of her own house & neighborhood, where everyone has black buttons for eyes. coraline's "mother" in this world wants her to stay there so she can take care of her forever. excitement, fantasy characters, and life lessons ensue.
hard to describe why exactly i liked it without giving things away, but it's able to get pretty dark & scary without losing its identity as a kids' book. the fantastical elements are very well-defined without dragging the plot down, coraline is a good strong central character, and every element feels it's in its right place. he does a lot with a very little amount of words, and it seems effortless in the way that most really good children's literature reads.