Unfortunately, I don't think any of the OO Churches have a good, reliable, and coherent catechism-type book published, at least in english, yet. I am working with others (others more learned and knowledgeable than I, including clergy) from my church (the Coptic Church) on a general OO catechism which considers all types of authority from all of the OO traditions, yet that is not likely to be finished for at least a couple of years (and even then, we are speaking about a very "basic" caetechism).
Nevertheless, you may be interested to consider, for now, The Syrian Orthodox Church: Its Religion and Philosophy (Kottayam: D.C. Press, 1973). This was authored by the late Metropolitan Athanasius when he was still a lay person under the name Dr. Paulos Mor Athanasius Kadavil. I had to order my copy directly from the Syrian Orthodox study centre at Kottayam, India. It's not the best, but it's better than nothing. H.E. frequently refers to the authority of the Syrian Orthodox Fathers however, so if your concern is Syrian Orthodox patristics you should find it insightful. The Fathers H.E. frequently refers to are: St Ephrem the Syrian, St Moses Bar Keepho (10th Century), Mar Gregorios Bar Hebraeus (13th Century), and St Dionysius Bar Salibi (12th Century), and a certain St Jacob (though I can't figure out which precise St Jacob this may be--the sub-professional standard of referencing doesn't leave one with any real clue).