It would be very silly indeed to argue that nonfiction writers are running out of ideas; the Samuel Johnson prize shortlist, to take just one guide, grows stronger with every year that passes. Nevertheless, I can't help but notice that we're in the midst of a sudden rash of books about books; I've read three in the past two months alone. The latest of these is by Rebecca Mead, a writer at the New Yorker, who has turned an essay she once wrote about her love for George Eliot's novel Middlemarch into a full-blown hymn of adoration comprising a lot of biography, a little literary criticism, and a teeny-tiny drop of memoir. Yes. What I'm trying to say is that if there is anything new in this book, I'm damned if I can find it.

But this is unfair. Mead didn't set out to hurl a boulder into the tranquil pond of Eliot scholarship. A passionate reader, it's her conviction that when a person is truly "grasped" by a book, it does not feel like an escape from life but a vital dimension of life itself: "There are some books that seem to comprehend us just as much as we understand them, or even more. There are books that grow with the reader as the reader grows, like a graft to a tree." Mead first read Middlemarch as a teenager in the seaside town from which she longed to escape ("Oxford was the immediate goal, but anywhere would do"). She fell for it hard – she couldn't believe how "relevant" it felt, and sought to identify herself with the intelligence she found within its pages – and she has returned to it regularly ever since, each visit enriched both by her experiences, and by the memories it stirs. In the bustle of Brooklyn, it takes her back not only to the English landscapes of her childhood, but to the "intensity and imagination of beginnings". Its influence on her has been profound. She believes – oh, crikey – that Middlemarch has "disciplined" her character.

Wanting to pass on the baton, or perhaps to offer kinship to those whose feelings for Eliot's masterpiece of provincial life are similarly ardent, she sets out to unpick the novel's themes of marriage, ambition and familial responsibility and to connect its most important crises and dilemmas to points both in its author's life, and her own. The result is somewhat laboured, for all that Mead knits her material together with great skill and in prose that is always lucid and sometimes soaringly beautiful. A long precis of a section of Middlemarch will be followed by a disquisition in which she ponders the inspiration for the doomed marriage of Dorothea Brooke and her deluded academic husband, Edward Casaubon (most likely Mark Pattison, the rector of Lincoln College, Oxford, and his wife Emilia Francis), or Eliot's relationship with her stalker-like Scottish fan, Alexander Main (as a concession to his epistolary attentions, Eliot allowed him to edit the mawkishly titled Wise, Witty, and Tender Sayings, in Prose and Verse, Selected from the Works of George Eliot), or the writer's feelings for the sons of her beloved companion, George Henry Lewes (Eliot did not meet Lewes until she was, by Victorian standards, middle-aged, and Mead sees her "unexpected" family as a key influence on Middlemarch's "tensile" strength). All this is punctuated with visits to places connected with Eliot – to Nuneaton, close to which she was born, and to Coventry, where she later lived with her father – and a few snatched glimpses of Mead's own life: the flight to Oxford and thence to New York; a love affair that goes wrong; marriage and motherhood.

The Road to Middlemarch is an intensely sincere book. It wears its earnestness like Sunday best, only rarely cracking a smile, and thanks to this, it feels brutal to criticise it, particularly if you're also, as I am, a lover of Middlemarch. But I'd be lying if I said it spoke to me. Who is it for? If a writer is going to rely wholly on the scholarship of others – Mead owes a great debt to Eliot's biographer Rosemary Ashton, and to many others – then she must bring something else to the library: a new angle, an outrageous opinion or, ideally, a surplus of style. As I read, I longed for the loopy wit and dogged honesty of Geoff Dyer, whose book on DH Lawrence is such a peculiar marvel (and I loathe DH Lawrence). The element of memoir in The Road to Middlemarch is so coy as to be pointless; its travelogues are pedantic and obvious (it's hardly surprising that Coventry has changed, or that the Strand in London, where Eliot lived as a young woman, is now awash with pizza chains). Above all, Mead's reverence for her favourite writer is sometimes just too much. "I feel defensive on her behalf," she writes at one point – and, boy, does she mean it. Late on, she quotes from a letter Eliot wrote on her honeymoon in 1879 (to the horror of many, Eliot married John Walter Cross, a friend 20 years her junior, shortly after Lewes's death), in which the writer complains about the "disgustingly coarse Belgians with baboonish children" with whom she was obliged to share a railway carriage. Disgustingly? Coarse? Baboons? Mead is disappointed. It is, she writes, "surprising and difficult to find Eliot so unappealing in moments like these". Is it? Leaving aside the fact that it's something of a relief to hear Eliot sounding a regular person rather than a paragon of virtue, it's hard not to worry for Mead at this point. The Lord knows how she must feel about writers with more… difficult personalities: Dickens, Larkin, Patricia Highsmith. Is she even able to read them? Virginia Woolf must have her rushing for the smelling salts.

Her reading of Middlemarch is close, generous and intelligent. There's wisdom in her analysis of the flaws and strengths of Dorothea, Rosamond, Mary, Ladislaw, Fred and all the rest; I appreciated her refusal to judge, to see the light and shade even in Casaubon (Mead is surely right to insist that the older one grows, the more one sees the fear in Dorothea's wretched husband as well as the pomposity). In turn, this reminds us of the wisdom of their creator, at least in terms of what she put on the page. But it's wrong to want Eliot herself always to be a veritable owl of morality, kindness and sense. Middlemarch is the best of her, not a facsimile of her soul.

As for reading a novel as if it were a manual, though I've often been guilty of this myself, one must be wary. Isn't it just a more intellectual version of the dreary argument that insists a book cannot be enjoyed unless the reader "likes the characters"? I admire Mead's ambition, her chutzpah: there's daring in appropriating a masterpiece like this. But sometimes she makes Middlemarch, that most capacious of stories, seem a lot smaller than it is.

Rebecca Mead is speaking at Foyles in Cabot Circus, Bristol, as part of the Bristol festival of ideas, on Thursday 20 March