Catch-22 by Joseph Heller — Read

Yossarian ran right into the hospital, determined to remain there forever rather than fly one mission more than the thirty-two missions he had. Ten days after he changed his mind and came out, the colonel raised the missions to forty-five and Yossarian ran right back in, determined to remain in the hospital forever rather than fly one mission more than the six missions more he had just flown.

Yossarian could run into the hospital whenever he wanted to because of his liver and because of his eyes; the doctors couldn't fix his liver condition and couldn't meet his eyes each time he told them he had a liver condition. He could enjoy himself in the hospital, just as long as there was no one really very sick in the same ward. His system was sturdy enough to survive a case of someone else's malaria or influenza with scarcely any discomfort at all. He could come through other people's tonsillectomies without suffering any postoperative distress, and even endure their hernias and hemorrhoids with only mild nausea and revulsion. But that was just about as much as he could go through without getting sick. After that he was ready to bolt. He could relax in the hospital, since no one there expected him to do anything. All he was expected to do in the hospital was die or get better, and since he was perfectly all right to begin with, getting better was easy.