Donald Robertson is a cognitive-behavioural psychotherapist and writer, who was born in Scotland but now resides in Canada. He is the author of six books on philosophy and psychotherapy, including Stoicism and the Art of Happiness and the forthcoming How to Think Like a Roman Emperor: The Stoic Philosophy of Marcus Aurelius.
Essential reading for the practicing Stoic.
The best books on Stoicism from this century.
If you read nothing else, read the essentials.