Letters from a Stoic

Letters from a Stoic was written around 60 AD by Lucius Seneca, an advisor to Emperor Nero. The book contains 124 letters written by Seneca to a friend. They read more like a diary and advice given to a friend rather than a hardcore philosophical discourse. That is not to say it lacks philosophy, but compared to Epictetus’ Discourses, it is more muted.
For those interested in Stoicism, Discourses by Epictetus is far better. Seneca’s book is more like an ancient diary with a Stoic lens applied to it.