Discourses and Selected Writings

This might have been the most useful book (that I've read so far) in my quest to understand stoicism. If you're interested in stoicism as a philosophy, there is no good reason to skip reading this book.

Enchiridion, which is included at the end of this book, is very concise and approachable as translated in this rendition; if you're curious about stoicism but not yet invested into reading books about it, you can read Enchiridion to get some idea about it.