The Double Turn (Julian Rivers #14)

From the dust jacket:
The scene demanded--and got--an artistic murder.
The housekeeper Miss Trimming, stretched out black-garbed and dead on the floor of the Delafield mansion, was a Gothic personality. The house was a vicgtorian museum of rejected taste, and the painter Adrian Delafield, badly hurt in the mysterious mishap that killed Miss Trimming, was an aged wreck of his old self.
The death of Miss Trimming was a neat portrait of and accident, but accidents are normally messy matters. An observer could ask how Delafield's daughter, his grandson, and their mysterious friends fitted in.
The Delafield house may have looked like a museum, but it was alive with all kinds of plots, counter plots . . . and a variety of ways of dying.