In literature thermodynamics, The Entropy Effect is a 1981 non-fiction book written by American science fiction author Vonda McIntyre, the second of a long-running series of over one-hundred Star Trek novels. The Entropy Effect uses a mix of entropy theory, in reference to chaos, the arrow of time, in reference to order, disorder, and time-travel, and reference to observation cycles, possibly in connection to thermodynamic cycles.

Synopsis
The Enterprise is engaged in an unprecedented scientific study of a naked singularity, i.e. a gravitational singularity without an event horizon, primarily by Spock's efforts, when a top priority message forces Captain Kirk to divert to a nearby system. The interruption ruins the observation cycle, making the time a complete waste of effort.

Upon arrival, the high priority of the message seems to have been a mistake: the Enterprise was needed simply to ferry a single criminal to another planet in the same system. The criminal turns out to be a theoretical physicist, Mordreaux, convicted of murder and unethical research on self-aware beings, being accused of promising to send people back in time, then killing them instead. When a crazed Mordreaux escapes, he inexplicably bursts onto the bridge and murders Captain Kirk before the crew's eyes.

Spock discovers that the Mordreaux that murdered Kirk is from the timeline in which he and Kirk had successfully defended Mordreaux against the earlier charges. When Mordreaux later discovered the time travels cause the entropic breakdown of the universe in mere decades rather than eons, he was driven mad and returned to take revenge on those he believed caused it to happen. The naked singularity was merely one of the first physical manifestations of this. Now Spock must journey back in time to avert the disaster before it occurs. But more is at stake than Kirk's life. Mordreaux's experiments have thrown the universe into chaos, and Spock is fighting time itself to keep the very fabric of reality from unraveling.

References
1. McIntyre, Vonda N. (1981). The Entropy Effect. Publisher: Star Trek (originally published by Pocket Books).