Letters from a Stoic

This edition of Seneca's Epistles unites all 124 of the letters in a single volume, complete with thorough explanatory notes, an appendix, and an index of the names referred to in the text.
The entirety of this compendium was penned by Seneca during his retirement and sent to his friend Lucilius Junior, a procurator of Sicily. At this late stage of life, Seneca held great experience in matters of both philosophy and governance, having served under the Emperor Nero for fifteen years.

Despite the conversational tone present in many of Seneca's epistles, it isn't entirely clear whether Seneca actually corresponded with Lucilius. It is possible that Seneca simply wished to write fictional correspondence so as to experiment with the form, possibly recreating how he wisely explained ideas or concepts to individuals.

The quotation: Vita sine litteris mors - 'Life without learning [is] death' - is derived from the 82nd epistle, and remains the motto for several educational institutions around the world.