"There is a major classic, which may suitably be called Gwendolen Harleth, hidden from the general recognition it deserves in the voluminous mixed work that George Eliot published … There can be few who have read Daniel Deronda to whom the idea has not occurred of freeing by simple surgery the living part of the immense Victorian novel from the deadweight of utterly different material that George Eliot thought fit to make it carry."
Thus asserted FR Leavis in an essay that brought some comfort to generations of readers struggling to find unity between the radically different strands of Eliot's unwieldy masterpiece. Her last novel, completed in 1876 and more than 800 pages long, Daniel Deronda yokes the riveting account of the spirited, egotistical Gwendolen Harleth, led by circumstance and her own wilfulness into a horrifyingly abusive marriage, to the more problematic (Leavis calls it "insufferably boring") journey towards self-discovery of saintly, handsome proto-Zionist Deronda. Harleth tries to make him her confessor, saviour and love object, while he himself is drawn to exploring his Jewish origins and doing battle against prejudice.
In her first novel, highly regarded biographer Diana Souhami takes up the gauntlet not quite thrown down by Leavis – who only ever suggested that Eliot might valuably have taken her own scalpel to the novel – and gives Eliot's beautiful, headstrong anti-heroine her own first-person narrative. This is as an act of breathtaking chutzpah: Gwendolen Harleth stands alongside Flaubert's Madame Bovary and Edith Wharton's Lily Bart as one of the most compelling characters in the history of the novel, and to assume creative responsibility for her is not for the faint-hearted.
Souhami's novel opens with the same mise-en-scene as Daniel Deronda: our heroine is gambling at the roulette tables of a German spa town when Deronda himself appears. Under his disapproving eye, her winning streak falters, and she falls in love. Souhami's overarching conceit is that this is the story of the "real" Gwendolen Harleth, a society figure upon whose travails Eliot drew for inspiration. Harleth refers to the spa town as Homburg, a real place visited by Eliot, rather than the fictional Leubronn: later Eliot herself, plain and clever, appears in the narrative to interrogate Gwendolen about her history and motives. Souhami's Gwendolen is telling her own tale, and not to Eliot but to Deronda: it is to him that her narrative – part monologue, part confession (in Eliot's novel, Deronda's crucial function is as a confessor figure) – is addressed. Thus, with one stroke Gwendolen is planted at the centre of the novel, while Deronda is relegated to her invisible interlocutor.
For two thirds of Souhami's novel, Gwendolen's extended, impassioned "letter" to the man whose love she believes will redeem her clings doggedly to the original. Both plot and significant dialogue are lifted from Eliot: the story of Harleth's marriage to the chillingly sadistic Grandcourt, the exchanges (with Deronda, with the greedy uncle who wants her safely married off, with Grandcourt himself) that lead Gwendolen to torment, and the appalling circumstances of her eventual liberation from it, are all brilliant – and all Eliot's.
Souhami approaches her own exploration of the sadomasochistic element to Gwendolen's relationship with Grandcourt only to shy away from it: there are glancing references to the "sexual humiliation" of their marriage bed, a phrase both inadequate and excessive. The story remains gripping, but the effect is bewildering: containing a great deal of indirect speech and brisk summary (which often takes the form of Gwendolen telling Deronda, rather improbably, things he already knows because he was present for them), it reads for these first 200 pages very much like a workmanlike abridgement of Eliot's novel.
It is a painstaking one, however, with some fine descriptive writing, and it is often clever. By making Deronda indescribable, for example – Gwendolen cannot very well tell him what he looks like – Souhami neatly points up the stubborn unreality of Eliot's character. And by moving Gwendolen on beyond Eliot's ending into the liberating world of fin-de-siecle Bohemianism and allying her to the suffragist movement, the author replaces Deronda's Zionism with a moral cause that sits more comfortably, if predictably, alongside her heroine's story.
Souhami's attempt is doomed – partly because summarily lopping Deronda out while allowing him to remain the focus of Gwendolen's outpourings leaves the narrative fatally unbalanced, and partly because Eliot's heroine is too perfectly characterised to allow for even the most delicate of tampering – but it is intriguing, and it is brave.
It also has the positive effect of sending the reader joyfully back to the original, to discover Eliot's wit, her leisurely, precise unfolding of character, her acuity and the towering genius that is undiminished, it turns out, for being flawed.
• Christobel Kent's The Killing Room is published by Corvus. To order Gwendolen for £13.59 (RRP £16.99) go to bookshop.theguardian.com or call 0330 333 6846.
