Withering heights / Dorothy Cannell.

Enhanced descriptions from Syndetics:

Ellie Haskell - the formerly plump girl turned Thin Woman and happily married mother of three - is also a sometime sleuth and a Gothic romance addict. When her husband's young cousin, Ariel, turns up unexpectedly and begs Ellie to come to the Yorkshire moors to investigate some strange events at the house that her family has recently bought with their lottery winnings, Ellie can't resist - especially since Cragstone House sounds so much like the delightfully musty manors she reads about inbooks.nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; And so Ellie and her husband set off for Yorkshire, accompanied by their irrepressible housekeeper and co-conspirator in crime solving, Mrs. Roxie Malloy, who happens to have a long-lost sister in the area. Things at Cragstone House are even more dire than Ellie expected. It's bad enough that the kindly cook, Mrs. Cake, has suffered a mysterious fall down the stairs, and a visiting vicar has keeled over dead while drinking acup of tea, but one of the neighbors turns out to be Mrs. Cake's husband's glamorous old flame, whom Ellie finds more menacing than any cold-blooded killer. Ellie has always thought it would be wonderful to be the heroine of a Gothic romance, but now she's beginning to wonder: Will she be able to solve the mystery and get out of Bronte country with her life, and her marriage, intact?