I think I would like to see some books primarily on their history since Chalcedon, their relations with EO and the Catholic Church, any theological works, and possibly some spirituality.
For a general overview of the history, doctrines and spirituality of the Coptic Orthodox Church in particular, I recommend:Meinardus, Otto. F.A., Two Thousand Years of Coptic Christianity
Malaty, Fr. T., Introduction to the Coptic Orthodox Church
El-Masri, Iris. H., The Story of the Copts, Books I, II & III
Of Other OO Churches:Kermian, M.,
Welcome to the Armenian Church  Guaita, G., Between Heaven and Earth (Armenian Orthodox Church)
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Doctrinal works:Ecclesiology:
Malaty, Fr. T., Unity of the Church and Church Sacraments
Paulos Mar Gregorios, The Meaning and Nature of Diakonia
Paulos Mar Gregorios, The Church and Authority
Tradition:
Malaty, Fr. T., Tradition and Orthodoxy
Pneumatology:
Malaty, Fr. T., The Gift of the Holy Spirit
Malaty, Fr. T., The Procession of the Holy Spirit
Sacramentology:
Malaty, Fr. T., Christ in the Eucharist
Kochakian, Fr. Garabed., The Sacraments: Symbols of our Faith ÂÂ
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Patrology:
Paulos Mar Gregorios, The Faith of our Fathers
Paulos Mar Gregorios, Cosmic Man: The Divine Presence - The Theology of St.Gregory of Nyssa
Malaty, Fr. T., The Apostolic Fathers
Malaty, Fr. T., The School of Alexandria: Before Origen
Malaty, Fr. T., The School of Alexandria: Origen.
Wahba, Fr. M., The Doctrine of Sanctification in St Athanasios.
Liturgics:
Malaty, Fr. T., The Church: House of God
Anjewac'i, X., Commentary on the Divine Liturgy (of the Armenian Orthodox Church).
Theology:
Koghbatsi, Y., Refutation of the Sects
Malaty, Fr. T., The Terms Physis and Hypostasis in the Early Church
Malaty, Fr. T., The Coptic Orthodox Church and Her Dogmas (Volumes 1-5).
Malaty, Fr. T., The Divine Grace
possibly some spirituality
Paulos Mar Gregorios, A Human God.
Paulos Mar Gregorios, Loves Freedom: The Grand Mystery
Paulos Mar Gregorios, The Human Presence
H.H. Pope Shenouda III, The Spiritual Man
H.H. Pope Shenouda III, The Release From the Spirit
Malaty, Fr. T., You Are My Delightful Garden!
their relations with EO and the Catholic Church
Attia, M., The Coptic Orthodox Church and the Ecumenical Movement
For relations with the Assyrian Church of the East:
H.E. Metropolitan Bishoy, A Documentary on the Nestorian Assyrian Church of the East: Its History, Present Conditions, and Doctrines.
In a past thread in here, someone recommended these two books:
The Council of Chalcedon Re-Examined
by V. C. Samuel
and
Christology After Chalcedon
by Iain R. Torrance
Are they reliable sources for OO theology?
Yes, especially the first one. Another good source is H.H. Sarkissian I,
The Council of Chalcedon and the Armenian Church.
For primary works of post-Chalcedonian OO theologians be sure to check out
www.orthodox-library.org.