The Dark Knight star reveals the Leo Tolstoy classic is one of her favourites, so she thought the job would be easy money.

"I thought, 'This will be amazing. I'll just sit in a room and re-read Anna Karenina out loud,'" Gyllenhaal recalls to The Associated Press. "I just loved the book so much I thought, 'Yes, let's try and do it.'"

However, Maggie soon learned the gig would be a lot harder than she had expected, so she decided to study up and read various different translations of the lengthy 1877 novel before she was due to hit the recording studio.

She explains, "A sentence will begin in one place and end really somewhere else. I couldn't cold read it. It just wasn't possible."

The extra homework for the Audible Inc. project ended up being a complete learning experience for Gyllenhaal, who is grateful for the opportunity to revisit the literary classic - even though the job took double the amount of time to complete.

"It was amazing," she admits. "I learned things about myself from reading the book in the way that I think a lot of people learn things about themselves from reading the book, whether its aloud or to yourself. And I learned different things about myself at 37 doing it than I learned when I was 25, which is also the mark of an amazing book."

Reading the book over and over again also inspired Maggie to take in more culture in her personal life, attending three plays and an art exhibit during her down time.

She adds, "I found when I was reading the book that my brain was being exercised in the same way that when you're running a lot you all of a sudden feel the strength in your body."