BOOK REVIEW: TRUE CRIME : Understanding the Mind of a Serial Killer : KILLING FOR COMPANY: The Case of Dennis Nilsen, <i> by Brian Masters</i> (Random House, $24, 317 pages)

As demonstrated most recently by the media’s fascination with Canada’s murderous “Ken and Barbie” couple, the most compelling true-crime stories tend to be the Dr. Jekyll and Mr. Hyde sort, wherein estimable citizens turn out to be steeped in iniquity.

In her “Pictures at an Execution” (Harvard University Press), critic Wendy Lesser speculates that we are drawn to such stories because they confirm our suspicion that there are hidden dark corners in our lives and in those of our loved ones.

Most true-crime books cash in on this suspicion by shining enough light on these shadowy corners to pique our interest but not enough to promote our understanding, thus heightening the provocative sense of danger.

Some true-crime books, though, attempt to pump up the wattage; like a parent shining a flashlight under a child’s bed, they aim to show us that real monsters exist only in our imagination.

“Killing for Company”--the story of Dennis Nilsen, contemporary Britain’s most notorious serial killer--is such a book. Faulting the true-crime genre for being “overwritten and often hysterical,” literary biographer Brian Masters suggests that this book will be worthwhile only to the extent that it “opens a window upon human behavior. . . . Otherwise, one is left with little more than a prurient titillating of the imagination.”

Masters’ aim--to show us “something of the nature of madness”--is indeed true. He wields all sorts of impressive psychological tools to understand why Nilsen felt compelled to kill 15 young men between 1979 and 1983. But as British psychiatrist Anthony Storr concedes in a postscript to these pages, even such swanky terms as “Borderline False Self as if Pseudo Normal Narcissistic Personality Disorder” ultimately fail to make sense of Nilsen.

Thus, we are sometimes left with what is indeed a “prurient titillating of the imagination.” Take, for example, the perverse but undeniably fascinating story of Nilsen’s behavior at a 1979 Christmas party he organized for his office, the Kentish Town Jobcentre.

A respected executive officer, Nilsen cooked and catered for 80 people, in galley pots he learned to use as a British army cook, then socialized merrily with colleagues. But when one of them put on a classic rock song that Nilsen had associated intimately with his lover, Nilsen cascaded into depression and felt compelled to leave.

Returning to his apartment, Nilsen shouted to his lover, “Right, if you want to listen to the music, then damn well come out and listen to it.” Removing the floorboards of his apartment, he pulled out his lover, whom he had killed two weeks earlier, and sat the body on a dining chair. Nilsen stood naked next to the body and trembled for many hours.

What Nilsen did with the other 14 men would put Anthony Hopkins’ Hannibal Lecter to shame. Suffice it to say that he boiled more than pub grub in those galley pots.

The easiest conclusion to draw from stories like Nilsen’s is: “Watch out! The world’s a scary place. It’s good to keep up your guard because these days, you never know who will turn out to be dangerous.”

But while Masters’ theories may be imperfect, they manage to show that Nilsen’s behavior arose not from some mysterious demonic possession, but from a predictable alienation that peaked when Nilsen began visiting a series of seedy gay bars to assuage his loneliness.

Finding London’s anonymous, fleeting gay scene to be no less isolating than the “fiercely cold” fishing village of his childhood, Nilsen, Masters writes, ultimately felt compelled to “kill for company, to have someone to talk to, someone to care for.”

This is, of course, an explanation, not an excuse. The fact that other people tread paths similar to Nilsen’s without reaching such Dantesque destinations leaves no doubt that Nilsen lacked something, whether it was willpower in his soul or neurotransmitters in his brain.

Nilsen was sentenced to life in prison. His trial, nevertheless, clearly exposed the primitive nature of the 1843 M’Naghten Rules that Western courts still use to determine mental derangement in such people. Because Nilsen knew that what he was doing was wrong, he was considered sane under those rules. After closely studying Nilsen’s life, though, Masters concludes that no adjective could possibly be more inappropriate.

In questioning such wisdom, Masters ultimately succeeds in his aspiration to go beyond titillation.