Like black lightning, he flashed:
In this scene we can see a simile being used by the author. Similes are sentences with like or as that the author uses to compare to something that means the same. For example I stepped on a rock, it felt like I stepped on a sharp needle. The sharp needle is comparing the amount of pain.
The pieces were as alike as two peas...
This another simile the author uses. He means by this that everything is off, spread around all over the show. I think this a very clever simile to use because peas are very spread around most of the time when you try to get them on your fork. And it makes a very clear image in your head.
Suddenly the whistle blew. It never began at full blast. It started hoarsely, as though clearing its throat.
Here the author uses another simile in this sentence. He means is that the person who blew the whistle made a sound so loud, and that none of the prisoners have heard someone blow the whistle as hard, so soon. For example I hanging out with some people and randomly blow the whistle as hard trying to make the loudest noise possible.