“[Sourdough] plunges through so much terrain: microbial nations, assimilation and tradition, embodied consciousness and the crisis of the tech industry, all without losing the light, sweet, ironic Sloanian voice familiar from Mr. Penumbra’s, a plot that makes the book a page-turner and a laugh-out-louder, with sweetness and romance and tartness and irony in perfect balance. What a great book, seriously.”