Originally a word for a slaughterhouse, shambles now usually means "one heck of a mess," as in "You were supposed to clean your room, but it's still a shambles!
When the job market is in a shambles, people have trouble finding work. When a supermarket is in a shambles, there might be melons and milk spilled all over the floor. If everyone in a classroom is talking and yelling at once, the class is a shambles, because no one can hear each other or get any work done. People say things are "in shambles" or "a shambles" — they mean the same thing. However you say it, a shambles is chaotic, disorderly, out of hand, and off the hook — a major, five-alarm mess.