The Paradise of the Holy Fathers is an excellent work. Although it was a Syriac text, it talks mostly about the Desert Fathers of Egypt (with some of the Greek Fathers thrown in there as well). I’ve read through the entirety of the first volume and most of the second (don’t know why I got bogged down in the second), and highly recommend the text to anyone/everyone. It’s by far the best work on the Desert Fathers that I’ve found. I even prefer it to the four-volume Evergetinos.
Not sure if the Coptics today have a catechism. I think you’ll find that catechisms in general are a rather modern phenomenon, and predominantly a Roman thing. Some of the Eastern/Oriental Churches do have catechisms, but most of them (that I’ve been able to find) are from modern 20th Century authors and mimic the Roman catechetical approach.
What you might consider looking for are the catechetical lectures of one of the early Fathers. Cyril of Jerusalem has some wonderful lectures that are quite challenging. Cyril of Alexandria also has some amazing homilies that serve as commentaries on the Gospel of Luke and the Gospel of John, plus some other wonderful writings as well.