Science fiction often portrays artificial intelligence in one of two ways. There’s evil AI — think HAL, the computer in “2001: A Space Odyssey,” who stops obeying orders from the humans so it can kill them. Then there’s good AI like Data in “Star Trek: The Next Generation” who gets lost in wonderment at the human ability to whistle. Martha Wells’ “Murderbot” doesn’t fit into either trope. This AI has a human face and shape. A layer of skin covers its mechanical and organic parts. But it doesn’t have sex organs: They’re not necessary for its job.