Letters from a Stoic is one of the most recommended philosophy books in modern nonfiction, serving as a primary source for the Stoic revival led by Ryan Holiday and widely endorsed by Tim Ferriss and his podcast guests. Holiday draws on Seneca's letters across The Daily Stoic, The Obstacle Is the Way, Stillness Is the Key, and his Stoic Virtues series, while Nassim Nicholas Taleb devotes significant attention to Seneca in Antifragile, calling him the original practitioner of upside-without-downside optionality.
Ward Farnsworth's The Practicing Stoic and Alain de Botton's The Consolations of Philosophy both treat the letters as foundational texts on death, adversity, wealth, and virtue. Readers consistently praise Seneca's directness and practical urgency -- these are not abstract philosophical treatises but actionable letters on manageing anger, grief, time, and mortality that feel startlingly modern.