The Spellmans Strike Again by Lisa Lutz.
Izzy is now 32, which according to everyone else, means she is an adult, and should probably start acting like one. So, she finally agrees to take over the family business.
This means that she has to buy some grown-up clothes so that she can meet with clients, like the eccentric millionaire Franklin Winslow, whose butler is missing.
But mostly, it's business as usual in her life. Her mother is trying to break up the relationship between Izzy and her Irish bartender boyfriend.
Her younger sister, Rae, has a new cause: to free a prisoner she believes has been wrongly convicted. Rae has a boyfriend, too, and he appears to be a drug-dealer.
Izzy's parents decide they need to have the house to themselves one day a week. Police detective Henry Stone suddently wants to be friends with Izzy.
David's new girlfriend Maggie appears to be suffering from morning sickness, and to top it all off, doorknobs and light fixtures are disappearing from the Spellman home/office.
This is the fourth book in the Izzy Spellman series, and I think it may be the best. It certainly evoked peals of laughter, which doesn't happen very often. Publisher's Weekly reports that this is the last book in the series, which is entirely possible, since several storylines seem to have ended.