"Duel to the Death" by Judith A l. Jance - eviltoast

I just finished this and figured it was worth sharing.

“After taking down the man responsible for his best friend’s death, Stuart Ramey finds himself left with a multimillion-dollar fortune in Bitcoin. It’s a desperate bid by Frigg, a rogue A.I. program created by the killer, to keep itself from being fully deactivated.”