A monastic rule of life might seem an unlikely bestseller but the Rule of St Benedict was almost certainly the most-read book outside of the Bible for five centuries around 1000AD.
In this kindle version, it is preserved in solid English, with a guide to reading it day by day. I haven't done that, but have found it ideal for dipping into, on the bus, or wherever your kindle takes you.
Its thoughts, whether about ordering your day, or how to say sorry, are maxims that have stood the test of time.
Worth getting a kindle copy if you're already a fan, and certainly worth purchasing if you've never heard it before.
This could be about the best 80p you ever spent.