There’s something a bit gruesome about the suggestion that everyone’s got a book inside them – you imagine it lurking, like the creature in “Alien”, somewhere behind the lungs and heart . But if you think you do, Scrivener is the app to tease it out. The desktop version has had a cult following for years but its vast battery of features is finally available on a mobile app. Designed to structure and edit, Scrivener placidly holds all your research, notes, pictures, fragments, sketches and web clippings as you shuffle them. A clever system of virtual binders and indexes removes most of the hair-tearing as you compile the final draft. This is a godsend not just for budding novelists but for anyone composing a document longer than a shopping list.