Hilary won the Theakstons Old Peculier Crime Novel of the Year Award in Harrogate on Thursday.
Radio Times TV editor Alison Graham, who was one of the judges, described the book as "an emotionally exhausting and powerful story".
US author Sara Paretsky, who created detective VI Warshawski, received an outstanding contribution honour.
The accolades were handed out at the start of the North Yorkshire town's annual crime writing festival.
Shetland and Vera writer Ann Cleeves, this year's festival programming chair, said the crime novel of the year shortlist had been "really strong" this year.
The panel had felt Hilary's winning book was "so finely written and tightly written", she said.
Someone Else's Skin, a thriller that tackles domestic violence and so-called honour crime, is the first in a series of novels featuring Det Insp Marnie Rome.
"The author was able to conjure up atmosphere in very few lines," Cleeves said. "The subject matter was well done and well plotted."
The other books on the shortlist were:
Sara Paretsky was chosen for the outstanding contribution to crime fiction award after her 23-year career writing about VI Warshawski, a female private investigator from Chicago.
Actress Kathleen Turner played VI Warshawski in a 1991 movie based on the Deadlock novel and in a BBC Radio 4 adaptation.
VI Warshawski was "a real game changer", Cleeves said. "This was a woman who didn't just solve crimes but was like an action hero in a sense."
Paretsky "really changed the way that readers thought about female writers", Cleeves said.
"When she started writing, it was pretty well unheard of to have a strong female protagonist," she added.
Paretsky also set up Sisters In Crime, an organisation to support female crime writers around the world.
Author Sarah Hilary has won one of the UK's top crime-writing awards for her debut novel, Someone Else's Skin.