Unless you absolutely cannot afford to, I firmly suggest to invest in a solid English translation. A bad translation is a deal breaker. For Seneca's works, I

Unless you absolutely cannot afford to, I firmly suggest to invest in a solid English translation. A bad translation is a deal breaker. For Seneca's works, I recommend these: → 'Letters on Ethics' (University of Chicago Press) – I consider this to be the definitive English translation; it's done by two of the foremost scholars: Margaret Graver and A. A. Long. This has the full set of 124 letters. It reads extremely well, has a solid introduction with excellent notes throughout, and it's also wonderfully typeset. It can't get better than this. (This costs about 40 euros; if it's a tad pricey for you, see the alternative below. ) → 'Seneca: Selected Letters' (Oxford World's Classics) — This is a curated list of letters by a reputed scholar, Elaine Fantham. A compelling aspect about this edition is that at the beginning of each letter there's a short summary of it. → 'Seneca: Dialogues and Essays' (Oxford World's Classics) — This contains some of Seneca's famous essays on bereavement consolations, on tranquility of the mind, and more. Translation by John Davie; it reads very well. (I also consult an alternative excellent translation, 'Hardship & Happiness'; this was also, like the full set of letters above, commissioned by Chicago University Press; and translated by several scholars.) And FWIW, I've written[1] last year about suggested English translations for broader Stoicism-related works. Translations matter. [1] https://news.ycombinator.com/item?id=22990579 https://news.ycombinator.com/item?id=22990579