Biographer Claire Tomalin's The Invisible Woman unravels Victorian author Dickens's 13-year romance with Ellen Ternan.
Never Let Me Go actress Carey Mulligan, Abbie Cornish and Felicity Jones are being considered for the role of Ternan, the Daily Mail reports.
Harry Potter star Fiennes is said to have considered playing the author of David Copperfield and Oliver Twist himself.
The actor directed and starred in his adaptation of Shakespeare's tragedy Coriolanus.
He is currently working on Mike Newell's adaptation of Great Expectations, which stars Helena Bonham-Carter and stage actor Jeremy Irvine.
Watch footage of Ralph Fiennes discussing Harry Potter and the Deathly Hallows: Part 2 at the film's press conference below: