Frugal innovation is becoming a common concept. Some authors define any ultra-low cost and resource-efficient product or service for poor people as a frugal innovation. They often use a single criterion proposed by Radjou and co-authors to differentiate frugal innovation. This article does not discuss this concept or its uses. It summarizes two books forming a frugalist diptych contrasting frugal innovation in poor countries (Radjou, Prabhu, Ahuja, 2013) and in rich countries (Radjou, Prabhu, 2015).JEL Codes: O31