“Confessions of a Sociopath” turns out to be an intermittently gripping and important book — albeit one that sags dramatically in the middle when the author goes on for ages about her not especially interesting childhood. (Here she tries to solve the nature/nurture mystery and concludes that she doesn’t know, but that her sociopathy is probably due to a bit of both.) Otherwise, it is a revelatory if contradictory muddle of a memoir in which she succeeds in simultaneously humanizing and demonizing herself.

Such is the intense stigma that comes with the label, it’s understandable she adopts a pseudonym. But it means we have only her word that Thomas is the woman she says she is: a sociopath as well as “an accomplished attorney and law professor,” who is just as comfortable “in summer dresses as I am in cowboy boots,” is super-popular — “in a world filled with gloomy, mediocre nothings,” people “are attracted to the sociopath’s exceptionalism like moths to a flame” — has “never had an insecurity,” feels no anxiety and possesses “remarkably beautiful breasts.” She rarely lets her pristine mask slip to reveal the gaping nothingness underneath.

Although the mask does slip sometimes. There was the occasion she came down with appendicitis and went to school in such pain she forgot to mimic her peers’ social niceties and instead “stared at them with the dead eyes I had previously reserved for when I was alone.” More recently, when a city worker berated her for using an off-limits escalator, Thomas found herself following him, a “metallic” taste in her mouth, fantasizing about murder and “how right that would feel.” She turned around only when she lost sight of him in the crowd. “I’m sure I wouldn’t have been able to actually kill him,” she says, “but I’m also relatively certain I would have assaulted him.” Although sociopaths are relentlessly self-interested, the logic of punishment frequently eludes them. They’re their own worst enemies — reckless, suffering poor precautionary controls,never learning their lesson. Thomas has lost count of the times she’s gotten sick from eating rotten food because the “risk of injury never sinks in.”

Despite all her claims of Spock-like rational genius, you are frequently reminded that this is a book written by a damaged person. For instance, there’s the implausible claim that although Thomas “has always lived in the worst neighborhoods,” she doesn’t need to worry about her pension because she’s one of the world’s greatest stock-market speculators, averaging a 9.5 percent return. “Beating the market this soundly and consistently is unheard-of,” she writes, putting her success down to her “special vision. When I look at the world, the flaws or vulnerabilities in people and the social institutions that they’ve made jump out at me.”

During passages like this it’s worth remembering that pathological lying and lack of realistic long-term goals are two of the items on the Hare checklist. And Thomas’s claims of leading a moral life are undermined somewhat by the cheerful accounts of some chillingly cruel deeds she’s committed, from leaving a baby opossum to drown in her swimming pool — “I did not give it a thought” — to the time she cut off all ties to a friend whose father was dying of cancer because the woman wasn’t fun to be around anymore.