One of the series that I'm most enjoying this year is The Blackbird Sisters Mysteries by Nancy Martin. She throws in quirky characters, a dubious boyfriend, parents who have left the country to evade the tax man and two sisters who pop up at unexpected moments. I'm only on No. 2 - Dead Girls Don't Wear Diamonds and there are six more currently in the series.
From the cover:
When a high society jewel thief winds up drowned in a pool with a tacky garden gnome tied to her ankles, ex-debutante Nora swings into action to save her old flame Flan Cooper from a murder charge. But then a politically ambitious millionaire with hushed-up secrets, a dotty grande dame with a penchant for polo teams and a cat fancier who keeps a gun with his silver tea set all steer suspicions onto Nora herself. Nora must find the killer on her own - or risk trading her grandmother's couture for an orange jumpsuit.