The 6th man by David Baldacci

After alleged serial killer Edgar Roy is apprehended and locked away in a mental facility private investigators Sean King and Michelle Maxwell are called in by Roy's lawyer--an old friend of Sean King--to look into the case. But their investigation is derailed before it begins: while en route to their first meeting with the lawyer, King and Maxwell discover his dead body. It is up to King and Maxwell to uncover the truth: is Roy a killer or not?

The book is based on a ridiculous premise of "the wall" so that although most of it is quite believable, the wall blows any credibility out of the water. Still, it was a good read.

Divine Justice by David Baldacci

This novel opens where Stone Cold ends, just after Oliver Stone
has assassinated Carter Gray, head of the CIA, and Roger Simpson, who
had raised Stone's daughter after his wife was murdered. Both men had
conspired to ruin Stone's life and force him underground courtesy of a
fake grave at Arlington National Cemetery. It was a righteous kill
within the world of the series. He is headed to New Orleans on Amtrak,
leaving his friends in the dark as to his destination, when a young man
on the train is attacked by three hoodlums. Stone rescues the young
man, but they have to leave the train. He accompanies the man to
Divine, which at first seems to be a good place to hide.