Epictetus' extant works have much to recommend them. The basic themes are that you are in control of your thoughts and behavior to a greater degree than you might think, you are less in control of others' behavior and other "externals" than you might think, and that fretting about what's not under your control will lead to unhappiness. It's not hard to quibble with the details and arguments he offers, but the basic picture he offers is very inspiring to me.

It's rather repetive, and it's not systematic. With books of this type, I like to read a bit each evening and then re-read the same bit the following morning. Upon the second read, I pick a passage and memorize it, repeating it to myself on occasion throughout the day. I'd be interested to learn whether others have similar habits.