Steampunk, a shapeshifting and unpredictable genre, has a way of subverting the past, mischievously disordering the universe with historical what-ifs. It’s a field not normally rewarded with prizes and critical hallelujahs. Natasha Pulley’s first novel, The Watchmaker of Filigree Street, proved an exception. In a gaslit London menaced by Fenian terrorism, Nathaniel, a wide-eyed innocent, met and fell for a Japanese watchmaker, Mori, who could remember the future.