Born out of the short story David Mitchell published on Twitter in 2014 and inhabiting the same universe as his latest bestselling novel The Bone Clocks, this is the perfect book to curl up with on a dark and stormy night. Turn down Slade Alley - narrow, dank and easy to miss, even when you're looking for it. Find the small black iron door set into the right-hand wall. No handle, no keyhole, but at your touch it swings open. Enter the sunlit garden of an old house that doesn't quite make sense; too grand for the shabby neighbourhood, too large for the space it occupies. A stranger greets you by name and invites you inside. At first, you won't want to leave. Later, you'll find that you can't.