Epictetus (65 A.D - 135 A.D) was a Stoic philosopher who talked primarily about ethics. The Enchiridion (or Manual, or Handbook) is a collection of his most important sayings. The Enchiridion is written in literary Koine Greek, and is highly recommended by both NT and Hellenistic Greek scholars. It's one of those works that one should read many times during your life.
Epictetus is well known for being down to earth and using everyday examples of life to illustrate his teaching. The Enchiridion is a collection of sayings, so one can read a little bit here and there. You won't miss half the story.
There is a website associated with the Enchiridion Study Group; the website includes an online bibliography, vocabulary pages, audio files and other content you are able to download. More content will be added as the group progresses.
Schenkl's Greek text for each week's reading is available as a pdf file, along with the texts and notes of Heyne, Schweighauser and Thurot. Each reading also includes a list of questions on the text. The site can be found at http://www.letsreadgreek.com/epictetus.