Black Dog by Stuart Woods

 Lawyer Stone Barrington gets a fabulously wealthy new client named Annetta, who just inherited a fortune from her late husband. She is worried her "black dog" of a stepson is going to kill her to get his hands on the fortune, so she has Stone change the will to give him a huge monthly allowance--as long as she's alive. Shortly after, Annetta turns up dead. The next heir turns out to be Stone's assistant, Joan. Which puts a target on her back. Stone and Joan are trying to stay one step ahead of the very wily stepson. Stone is also trying to stay out of the cross hairs of the irate ex of his newest squeeze. Lots of threats everywhere.

This one actually had a better plot than some of the recent Stone books plus a good, albeit abrupt, ending.  I do love the character of Joan.