‘Walking by the banks of the Chao Praya on a breezy evening after a day of intense heat,’ writes Sunil Amrith at the start of his melancholic new book, ‘I struggled to connect the scene before me.’ While the river that flows through Bangkok looked idyllic, ‘crowded with noisy pleasure boats festooned with lights’, Amrith was struck by the realisation that half of the city ‘could be underwater by the end of this century’.