I have been completely gripped this week by my latest Persephone treat, Harriet by Elizabeth Jenkins, and my high expectations were amply fulfilled.

The real Harriet, to mark her engagement in 1874

Jenkins, who only died two years ago, aged 100-and-something, was fascinated by Victorian crime and especially the chilling horror of domestic crime. Harriet is based on the real-life Penge Mystery, a sensational murder trial that gripped the nation in 1877. Harriet is mentally disabled, a 'natural' they would have said in those days, but she has been brought up as a fastidious lady by her loving mother - she loves fine clothes - and she has a substantial fortune of her own. On a visit as a paying-guest to distant, impoverished cousins, she falls victim to a fortune-hunter who marries her against her mother's will. Lewis was previously courting Alice, one of the cousins, whose older sister is married to his brother Patrick, an impecunious artist, in whose eyes Lewis can do no wrong ... and before too long, Lewis and Alice are living in some style as husband and wife, on Harriet's money, while Harriet and her baby are starving to death in a squalid attic at his brother's house in the country.

Harriet and her baby? Oh, yes ... it is typical of Jenkins' laconic style that she drops this in so casually, bringing the reader to a sudden jolt of realisation that Lewis has consummated his marriage to poor Harriet, how confused she must have been and how terrified giving birth to a child. Perhaps he thought it wiser to consummate the marriage so it couldn't be annulled ... and then Harriet was available, so why not, her silly devotion flattering to his vanity, and he didn't find her repulsive ... or at least he didn't yet.

There is no conspiracy to kill Harriet ... it's more a creeping wickedness of neglect and, as in her later book Dr Gully - also based on a true Victorian murder-scandal - Jenkins is brilliant on what goes on behind closed doors, out of sight of respectable society.

And although I know I'll be howled down for this, her brilliance as a writer is that she does moral ambiguity so well. In The Tortoise and the Hare, one of the best novels I've ever read about marital infidelity, she allows you to sympathise with each of the characters ... the devoted, insipid wife, her Alpha-male husband and the voracious spinster next door.

What happens to Harriet is undoubtedly wicked, but Jenkins allows you to get under everybody's skin, so although you can't exactly sympathise, you can begin to understand. How Alice is envious of lumpish Harriet in her beautiful silk gowns ... who wouldn't be? How Patrick's wife would do anything in the world for her husband and family. But of course she resents Harriet's intrusive presence in her home ... wouldn't you? How they are each of them trapped in barely genteel poverty on the lowest rungs of the Victorian middle class. Can't you just imagine Lewis, as an impoverished clerk with dreams, investing in a 1d copy of self-help guru Samuel Smiles - and embracing its message rather too well?

And at the end, we're left wondering are they guilty? Morally guilty, without a doubt. But guilty of murder?

No great surprise that Kate Summerscale chose this as one of her books of the year in yesterday's Guardian. Jenkins is wonderful on Victorian detail - food, furnishings, clothes - and I wonder if that's because she was writing in the 1930s. Close but not too close. A contemporary writer might have taken it for granted; wouldn't have bothered mentioning how Harriet fastidiously combed out her fake hair every night. (One of the shocking details later is that her real hair has become hopelessly tangled and matted into her wig.) 

I'd love to track down some more of Elizabeth Jenkins. Apparently, she wrote 12 novels - but despite keeping an eye out in charity shops, I've only ever managed to find Dr Gully, Jenkins' own favourite. Apart from the two that are still in print, of course. I enjoyed it, but I much preferred Harriet.