Primary source
Letters from a Stoic (Epistulae Morales ad Lucilium)
Written by Seneca · 65 · grounds Lucius Annaeus Seneca
Overview
124 letters written to Seneca's friend Lucilius, governor of Sicily, in the last three years of Seneca's life. Each letter takes one practical idea (time, friendship, anger, crowds, death) and works it down to something you can do today. The single most readable Stoic text ever written.
A full write-up of this book has not been published yet.
Skills drawn from this book
Installable Claude Code skills grounded in this text. Each one teaches a framework the book actually argues for.