How does the lawyer spend his 15 years of imprisonment in "The Bet" by Anton Checkhov?

The impulsive lawyer is sequestered in the banker's lodge where he can have virtually anything he desires except human companionship.

After arguing against the banker that life imprisonment is not less humane than capital punishment--"to live anyhow is better than not at all"--the banker wages two million rubles that the lawyer cannot stay in solitary confinement for five years. With the arrogance and recklessness of youth, the lawyer contends that he can stay, not just five, but fifteen years. The banker accepts the bet, but he warns the younger man,

Don't forget either, you unhappy man, that voluntary confinement is a great deal harder to bear than compulsory. 

So, while the lawyer tries to prove that living an isolated life is not a hardship and win the bet of two million, he can have any of the books he wants, he is given a piano and music, he is allowed to write letters, and he may drink wine and smoke. The only outlet to the outside is a little window through which the books and letters and other things are passed. 

During the first year, the prisoner is extremely lonely; he spends a great deal of time at the piano. Because he is lonely, he refuses the wine and tobacco; in explanation, he writes that wine stimulates the senses, only exacerbating his lonely condition. Tobacco ruins the air of his little room.
In the second year, the prisoner stops playing the piano, and he exchanges the light reading of his first year for the classics. Then, in his fifth year, the prisoner requests wine, and he again plays the piano. During this year, the lawyer mostly eats and drink and lies on his bed. But, at times he writes all night; afterwards, however, he tears up what he has written, crying. 
Then, in the sixth year, he begins to study languages, history, and philosophy. He immerses himself in these studies so much that the banker is overwhelmed as he tries to furnish the books. After the lawyer learns six languages, the prisoner writes his jailer in these languages; further, he requests that the banker show them to experts and fire a shot in his garden if they are correct. The banker follows the lawyer's instructions and fires two shots. Hearing these shots, the lawyer expresses his happiness since he has mastered six hundred volumes of scholarly learning.
After the tenth year, the lawyer abandons all reading, but the Gospels. Theology and philosophy are his next readings. In the last two years of his confinement, the lawyer reads indiscriminately, choosing Shakespeare, then a medical manual, then philosophy or theology.

His reading suggested a man in the sea among the wreckage of his ship and trying to save his life by greedily clutching first at one spar, and then at another.

Before he is released, the lawyer, now a man of despair, writes that he despises freedom, life, and health--all that is called "the good things of the world."