The prisoner, a young lawyer, spent the final two years of confinement reading. He read books on topics such as philosophy, religion, science, literature, and medicine. The banker recounts that the young lawyer read avidly and voraciously, incessantly moving from text to text. Apparently, the lawyer has resolved to survey the span of accumulated human knowledge.
Your second question asks if the prisoner (the lawyer) was set free. The lawyer had been free to leave at anytime during the fifteen years. He would, of course, have to forfeit the two million dollars. Because he researched the wisdom of the world, he determines that despite any human success or accomplishment, life is futile. He states that mice and men have the same fate because they all eventually die. He no longer values money or achievement, so he leaves the lodge a few hours before the fifteen years end. Neither man dies.