A lot has to go wrong for the world to turn into an alt-physics realm of vertically-distributed islands, hovering in a breathable atmosphere, populated entirely by amnesiacs. Clearly those things have gone wrong at the beginning of Will McIntosh’s clever and absorbing novel, Faller, and much of the forward momentum of the story is fueled by the reader’s desire to find out how things could have ended up in such a disastrous and improbable state. I am a great admirer of several of McIntosh’s previous books, which are built on a foundation of big ideas, but always propped up by vivid and believable characters. Faller very much continues in that tradition. On what comes to be called Day One, when a man awakens on what seems to be a broken and floating chunk of a city. The man has no knowledge of who he is, where he is, or why the world is full of inexplicable machines, whose purpose no one can remember. The clueless inhabitants face a number of obvious crises, most pressing among these being distressingly-limited amount of food, which more or less instantly generates a Hobbesian struggle for survival. In his pockets, our protagonist finds three things…