The new book is Rowling's first foray into non-fiction and the closest to self-help the author has come in her distinguished writing career.

It draws from a seminal commencement speech she gave at Harvard University in 2008, based around the importance of failure and how we can use imagination to better ourselves (scroll down for the video).

Rowling famously rose from impoverished single mother to world-famous author on the back of her Harry Potter franchise. She now has a net worth of £570 million and book sales of 450 million worldwide.

But she's at pains to point out that this transition was not the straight-forward fairy tale it's been portrayed as; when she hit "rock bottom", she had no idea what lay ahead.

"I’m not going to stand here and tell you that failure is fun," she writes. "That period of my life is a dark one, and I had no idea that there was going to be what the press has since represented as a kind of fairy-tale resolution.

"I had no idea then how far the tunnel extended, and for a long time any light at the end of it was a hope rather than a reality."

JK Rowling describes hitting 'rock bottom' in a new book about the benefits of failure