There have been 2 reviews of TCCG so far in the American press, both in trade papers; Booklist and The Library Journal both gave The Cold Cold Ground starred reviews and you can read those if you scroll down past the blogposts about Vertigo and Downton Abbey. TCCG came out in the British Isles in January and here are some representative views of the British and Irish press:
...
"If Raymond Chandler had grown up in Northern Ireland, The Cold Cold Ground is what he would have written." --Peter Millar, The Times
"Written in a terse style, the novel is a literary thriller that is as concerned with exploring the poisonously claustrophobic demi-monde of Northern Ireland during the Troubles, and the self-sabotaging contradictions of its place and time, as it is with providing the genre’s conventional thrills and spills. The result is a masterpiece of Troubles crime fiction: had David Peace, Eoin McNamee and Brian Moore sat down to brew up the great Troubles novel, they would have been very pleased indeed to have written The Cold Cold Ground." --Declan Burke, The Irish Times
"Tropes are tropes for good reason. The important crime-fiction ones are present and accounted for here -- a serial killer who purposely leaves clues, a cop who's on to him, procedural and forensic nitty-gritty. Yet McKinty can startle with bouts of lyrical scene-setting that could only come from the fingertips of someone who grew up in the environment. He tells us of "arcs of gasoline fire under the crescent moon... The scarlet whoosh of Molotovs intersecting with exacting surfaces. Helicopters everywhere: their spotlights finding one another like lovers in the Afterlife". He educates us about shopkeepers boarding-up their windows when a riot was due, or the ritual of paramilitaries leaving a silver 'Judas coin' by the corpse of a bumped-off informant. Your reviewer was born the year The Cold Cold Ground (a Tom Waits' lyric, by the way) is set in, and such passages work better at painting a picture than any episode of Reeling In The Years." - The Irish Sunday Independent