Duel to the Death by J.A. Jance

I'm new to this series, having picked up the previous volume unaware of the premise or characters. But I jumped right in and have enjoyed the ride. Duel picks up where the previous book left off. Frigg the AI system created by a devious criminal genius, had freed herself from her creator and attached herself to Stu Ramey of the High Noon cybersecurity firm in Arizona. Stu thought she was too dangerous to have around, so he shut her off. Then he was notified that Frigg had bequeathed all of her (now dead) creator's fortune to Stu--but he'd have to turn her back on to get access to the money so he could pay taxes on it. Which put Stu and High Noon in quite a pickle. Added to this, Stu is contacted by a woman in Panama who says she was working with the AI creator and wants to continue working with him. But Stu begins to think she has a more nefarious plan in mind.

It's really quite the page turner, with drug cartels and murders and an AI system with a mind of her own that Stu is trying to retrain to use her powers for good instead of evil. Good summer read.