I finished Nightfall by Stephen LEather last night, and moved onto Midnight by the same author.
The books are books 1 and 2 in the "Jack Nightingale" series, about a former Police negotiator turned private eye who inherits a country house and estate under unusual circumstances. In the first book he has to come to terms with the fact that his biological father sold his soul to a devil. In the second he has to find his half sister and try and save her from the same fate that threatens him.
Well written, there are one or two timeline issues, but that doesn't, really, affect the overall story.