I often hear people say something like “the room is in shambles.” This is an improper use of the word, but everyone knows what the speaker means—the room is a chaotic mess.
The basic meaning of shambles is “slaughterhouse.” By extension, it can refer to a scene of slaughter or bloodshed —a Civil War battlefield perhaps—or, by somewhat greater extension, a chaotic mess. It would be perfectly correct to say that “the room is a shambles.”
In shambles, however, makes no sense. In a shambles would make sense but likely wouldn’t mean what the speaker thinks it does. There is, by the way, no such thing as a shamble. (The verb to shamble, on the other hand, means to walk clumsily with dragging feet. The verb is unrelated to shambles.)