Hopefully this qualifies for the sub.
https://www.amazon.com/Twelve-Months-Monastery-Victor-DAvila-Latourrette/dp/0767901800
The recipe book in question, a great book with an emphasis on simple, easily acquired ingredients. I've had many soups from this book and they're all solid, easy recipes at the very least.
http://www.amazon.com/Twelve-Months-Monastery-Victor-DAvila-Latourrette/dp/0767901800
This is a staple in my home both in and out of the fasting seasons. Not everything is 100% compliant with the rules, but can be made so with a bit of modification. Also, these recipes make big honkin' batches. Monks must be hungry people.
If you want variations on that theme. http://www.amazon.com/Twelve-Months-Monastery-Victor-DAvila-Latourrette/dp/0767901800 has a number of good potato leek type soups. and lots of others.