He is so stern.

It's not according to his years." At other times she thought: "Maybe he has become interested in some of a girl down there." But to go about with girls, money is needed, and he gave almost all his earnings to her.
Thus weeks and months elapsed; and imperceptibly two years slipped by, two years of a strange, silent life, full of disquieting thoughts and anxieties that kept continually increasing.
Once, when after supper Pavel drew the curtain over the window, sat down in a corner, and began to read, his tin lamp hanging on the wall over his head, the mother, after removing the dishes, came out from the kitchen and carefully walked up to him.

He raised his head, and without speaking looked at her with a questioning expression.
"Nothing, Pasha, just so!" she said hastily, and walked away, moving her eyebrows agitatedly.

But after standing in the kitchen for a moment, motionless, thoughtful, deeply preoccupied, she washed her hands and approached her son again.
"I want to ask you," she said in a low, soft voice, "what you read all the time." He put his book aside and said to her: "Sit down, mother." The mother sat down heavily at his side, and straightening herself into an attitude of intense, painful expectation waited for something momentous.
Without looking at her, Pavel spoke, not loudly, but for some reason very sternly: "I am reading forbidden books.

They are forbidden to be read because they tell the truth about our--about the workingmen's life.