There are books you grow up with and books you grow into. For the writer Rebecca Mead, Middlemarch was one of the former; for me, it was one of the latter.

Mead first fell in love with Middlemarch when she was 17 and preparing for her university entrance exams; three decades later, George Eliot's greatest work still speaks to her in fresh and profound ways.

In her moving and insightful new book, The Road to Middlemarch: My Life with George Eliot (Granta, £16.99), Mead traces her relationship with the book while exploring both the text and its author's extraordinary life. And in doing so she reminds us that some books are transformed by rereading, revealing more layers and complexities as we pass through stages in our lives: "There are books that seem to comprehend us just as much as we comprehend them, or even more. There are books that grow with the reader as the reader grows, like a graft to a tree."

I too first began reading Middlemarch when I was 17, but unlike Mead I didn't get very far. I found the painfully moral heroine, Dorothea, annoying and her unwise marriage to the scholar Causabon repellent. But what stopped me reading further was my foolish assumption that Dorothea's humourless high- mindedness was the author's.

I failed to see the affectionate mockery in Eliot's declaration that Dorothea felt that she enjoyed horse-riding "in a pagan sensuous way, and always looked forward to renouncing it". I didn't realise that, as Mead points out, Middlemarch is essentially "a book about young people for older people", who can look with empathy at the mistakes and failures not just of youth but also of middle age.

I eventually read Middlemarch in my 30s, partly inspired by a New Yorker piece by Mead that would eventually become her new book. This time I loved it – and, more importantly, felt I understood it in a way I couldn't have done when I was younger.

I also felt my sympathies expanding as a result of Eliot’s humane and wise view of human nature. Rebecca Mead’s book is a brilliant evocation of the role books can play in growing up, but it’s also a reminder that this process doesn’t end with the onset of adulthood.