J.K. Rowling is on the verge of releasing her first book meant for grown ups, The Casual Vacancy, but she's barely done any marketing for it. So it's kind of important when she gives a long, wide ranging interview with The Guardian.

Mum's been the word on The Casual Vacancy so far, but Rowling agreed to an exclusive interview with The Guardian's Decca Aitkenhead. Security's been so tight around Rowling's new book that when French paper Le Monde heard about the interview, they "dispatched a reporter to investigate how it was secured," says Aitkenhead. The two talk about the new book, Rowling's life, and whether or not she's read 50 Shade of Gray

But our favorite part of the interview is when she reveals how she came up with the idea for The Casual Vacancy:

Rowling has written seven Harry Potter books, and sold more than 450m copies, but her first novel for adults is unlike them in every respect – unless you count the location where the concept came to her. "Obviously I need to be in some form of vehicle to have a decent idea," she laughs. Having dreamed up Potter on a train, "This time I was on a plane. And I thought: local election! And I just knew. I had that totally physical response you get to an idea that you know will work. It's a rush of adrenaline, it's chemical. I had it with Harry Potter and I had it with this. So that's how I know."

Rowling famously came up with the idea for her last series of books, the one about the wizards, by scrawling ideas on a napkin while riding the train. It seems she gets her best ideas while travelling. We sleep while travelling on planes, trains or automobiles. Every time. We don't get ideas for multi-zillion dollar book franchises.

Read the rest of Aitkenhead's interview here. It's bloody long, but more than worth the time.