Anchorite by Randall Garrett, Science Fiction, Adventure, Fantasy (Paperback)

The mountain was spinning.

Not dizzily, not even rapidly, but very perceptibly, the great mass of jagged rock was turning on its axis.

Captain St. Simon scowled at it. "By damn, Jules," he said, "if you can see 'em spinning, it's too damn fast!" He expected no answer, and got none.

He tapped the drive pedal gently with his right foot, his gaze shifting alternately from the instrument board to the looming hulk of stone before him. As the little spacecraft moved in closer, he tapped the reverse pedal with his left foot. He was now ten meters from the surface of the asteroid. It was moving, all right. "Well, Jules," he said in his most commanding voice, "we'll see just how fast she's moving. Prepare to fire Torpedo Number One!"

There are two basic kinds of fools -- the ones who know they are fools, and the kind that, because they do not know that, are utterly deadly menaces!