What do you do when you've already sold over 36 million copies of your Horrible Histories books? You write the kind of book that you, as a reader, would kill to read. And Terry Deary's first love was always murder mysteries, so this year he brings us his first: Actually, I'm Murderer. We sat down with him to discover more about the incident in 1974 that inspired it, how he found his way to writing and what keeps him inspired.