Unless you’re the type who purposely searches out snippets about disasters, you go your whole life hardly ever hearing about the Triangle Shirtwaist Fire — a 1911 inferno in an overcrowded New York sweatshop which resulted in the deaths of many poor young female workers. And then suddenly, about five years ago, boom: Like the fire itself, retrograde interest in the fire ignites. Crosscutting back and forth from past to present and back, this fictional investigation into the amazing survival of a certain seamstress isn’t the first recent book about the debacle. Just by being a novel, it will dispirit readers who prefer their history pure and unsullied by imaginary characters and invented dialogue — though the survivor’s first-person narrative, told in refreshingly artless language, is the easiest-reading bit. Weber’s real-life grandmother sewed buttonholes at Triangle, albeit two years before the fire, which adds a bit of intriguing backstory. But it takes a true fan of modern literary fiction to warm up to this novel’s main thread in which a contemporary composer is creating an opus based on fractals, Sierpinsky triangles, post-tonal composition, human DNA, the Boulez aleatory creations — and the Triangle Fire.