As of 2016, Kelly has written fourteencrime novels. His first series began with The Water Clock, featuring fictional journalist Philip Dryden, based in the Cambridgeshire area of Great Britain. Kelly won the CWA Dagger in the Library Award in 2006 for the Dryden books. His new series, based on Detective Inspector Peter Shaw, is based on the North Norfolk coast and in the port of Lynn. In 2010 Kelly won the New Angle prize for literature for Death Watch, the second in the Shaw and Valentine series.
He is married to the biographer Midge Gillies and they have a daughter together.