@oristarA,
For language studies written in American, the non-intellectual detective stories by Robert Crais, Michael Connelly, and maybe Nelson DeMille. They use a reasonably wide vocabulary of everyday words, but won't send you to a dictionary so often that you lose the sense of the story.
For military fiction, Harold Coyle is as good as it gets.
For romance novels, Nora Roberts is probably a good choice.
Edit to Add: Stay away from science fiction, horror, and fantasy. They have their own vocabulary that is simply other worldly.
My suggestions on authors is based on readability, not elegance.