What I like about Denise Mina's writing is that she doesn't judge her characters, or write about them condescendingly -her characters are not 'good' or 'bad', and all have their reasons for acting the way that they do. As she showed in the Garnethill trilogy (highly recommended), Mina is acutely attuned to characters' mental states and this creates a multi-layered and complex cast of people who all play some part in how the narrative unfolds. She humanises characters, whether the perpetrators of the crime or the victim whose death kickstarts the narrative. The victim is often underwritten and underdeveloped in crime fiction -the reader usually encounters them after death, when all that can be offered up are bland platitudes from friends and colleagues (something that exasperates DS Alex Morrow when she is trying to get a sense of the dead woman's personality). But in 'The End of the Wasp Season', Morrow's attempts to piece together something of the victim, to add a human dimension to get her team interested (class and profession distance the dead woman from the people investigating her death), render the dead woman lifelike once again. There are a couple of sequences where we experience Sarah Erroll as she was in life (through recordings that are listened to / watched by Morrow, or someone who really knew her), and she is humanised: "It struck Morrow very suddenly: Kay was right. Sarah Erroll wasn't just a battered jigsaw puzzle. She was a young lassie and she was dead. It was sad."
The other aspect that sets Mina apart is that the police investigation (and the character of Morrow) is only one facet of the narrative; chapters alternate between different points of view, such as the perpetrator, and others who find their lives touched by the impact of the crime (it doesn't simply go back and forth between police and perpetrator -there is a sense of the ripple effect that a crime and its aftermath have). I read an interview with Mina recently where she said that she is not much of a plotter, and admittedly the reader does know who committed the crime from early on in the book (it's not a whodunnit), but the way that people's lives are interwoven around events is skillfully done and I think that it makes the narrative more compelling.
The way that Mina structures the book around several characters means that you can't really describe Morrow as the protagonist because equal emphasis is given to others as well, but she is the route into the story for the reader. This is the second book to feature DS Alex Morrow, but you don't need to have read 'Still Midnight' first (although this book may pique your interest in the first book). I found 'The End of the Wasp Season' to be a compelling read.