When you think about it, nothing could be less logical than to put all mystery fiction under a single heading. What does a cerebral sleuth like Sherlock Holmes have in common with noir gumshoe Philip Marlowe? How does a serial-killer shocker resemble a tidy puzzle from Agatha Christie? They have murder in common, but little more.

Denise Mina’s mysteries are in a category all their own (call it Gritty Scottish Urban); they push so insistently against the boundaries of the genre that I would hesitate to group them with anyone else’s work. They are brilliantly written, first of all (not a lazy sentence in sight); more important, they really take on crime: its roots, varieties and consequences. Her murderers are not necessarily villains, and her detectives rarely heroes of the conventional sort. Add a harsh setting like Glasgow, where Mina lives, and it’s difficult to call her books escapist in any sense. THE RED ROAD is, I think, even bleaker than its nine predecessors. Which is not to say it isn’t wonderful. Just don’t expect a tame thriller.

This is the third of Mina’s novels about Detective Inspector Alex Morrow, a woman as complicated as her cases. Morrow isn’t well liked by her coworkers, partly because she turned in a dishonest cop (who happened to be her partner), partly because she is a woman, partly because her brother is a gangster, and partly because she refuses to compromise --- not a good quality if she wants to be promoted to an administrative post. Not to mention that motherhood (she has twins) does not really mesh with police work: “She was spread so thin that she could feel her hard-won career running through her exhausted fingers.”

"THE RED ROAD is more demanding than most mystery novels because it is the very opposite of formulaic. In fact, reading it is a bit like doing a jigsaw puzzle when you don’t have the box that shows the complete picture."

The “Red Road” of the title is the location of a condemned 27-story Glasgow housing project that is being stripped for demolition. On her way to a murder scene on the 11th floor, Morrow must endure a terrifying climb on a concrete staircase unshielded by walls (even if you aren’t an acrophobic like me, you will find this sequence as chilling as any homicide). But I think the vivid phrasecould refer just as well to the whole bloody trail she is following through the city’s mean streets.

As always, Mina’s cast of characters runs the gamut of class --- from secret wrongdoers who masquerade as respectable people with law degrees and fine houses, to victims of poverty and abuse who become further victims when they kill. At the start, it is 1997, and we find ourselves inside the head of one Rose Wilson, a 14-year-old who is being pimped out by a lowlife named Sammy. Rose commits two murders in a few searing pages. What will become of her? Will she grow up to be a reformed citizen or a time bomb?

Flash forward 15 years, to DI Morrow and a baffling case of mixed-up fingerprints. Gradually it emerges that the wrong person got put away for one of Rose’s murders, but it isn’t a bit clear who engineered the fix, or why. A couple of crooked lawyers --- one dead, the other half dead with alcohol, guilt and loneliness --- seem to have had something to do with it. The dead lawyer’s son, having unearthed his father’s criminal secrets and called in the authorities, is running for his life (Rose, now 29, is a nanny for his children). Finally, there are a number of bent and/or passively complicit policemen who helped to orchestrate the original cover-up.

Whew! THE RED ROAD is more demanding than most mystery novels because it is the very opposite of formulaic. In fact, reading it is a bit like doing a jigsaw puzzle when you don’t have the box that shows the complete picture. It moves back and forth between time-frames, jumping from one character’s point of view to another. Sometimes it gets dizzying.

But Rose Wilson and Alex Morrow kept me reading even when I felt a little lost. They are parallel figures in a way, though on opposite sides of the law, each an ambiguous mix of toughness and vulnerability.

Rose is a character both scary and poignant, ruled by “fiery loyalties” and flashbacks to scenes of horrific abuse. At one point she compares herself to the serial killer Aileen Wuornos, with a similar background of sexual enslavement and a similar hunger for attention. Yet she is also a trusted part of a middle-class household, with genuine affection for the children she tends and a tortured sense of what she has done to survive.

Morrow, in turn, always seems to be wrestling with the tension between heart and head, truth and falsehood, right and wrong. At the end of the book, she makes choices that are unlikely to seal her professional success. Maybe that is just as well, as she doesn’t seem cut out to be a bureaucrat: “She couldn’t stand the thought of the rest of her career being a careful, backwards tiptoe to the door, telling the right lies to the right people.”

Is THE RED ROAD Morrow’s final appearance? Perhaps. So far, the author has never used a recurrent character in more than three novels: a wise policy, in my opinion (too many mystery writers stay with the same detective far too long). But even if Alex Morrow does not return, Denise Mina’s Glasgow surely will --- along with a new and intriguing protagonist for her tales of the city.