The first rule of making movies based on novels: it is more important to make a good movie than to be faithful to the book. I liked John Grisham’s novel "Runaway Jury" a lot. It is a very good novel. The film version, perhaps because it does not faithfully represent the novel, is also very good.
"Runaway Jury" is a taut thriller about a couple who manipulate a jury during a lawsuit against a gun manufacturer. It tips its hand too early in a couple places, releasing suspense but counters by giving us more interesting characters more than we might expect in a courtroom thriller.