The Odes of Solomon is recognized as the earliest Christian hymnbook. Questions, however, abound. Are the Odes essentially Jewish, Jewish-Christian, gnostic, or simply Christian? There is wide agreement that the Odes are related in some way to the Dead Sea Scrolls and the Gospel of John. Charlesworth argues that the Odes were composed in an early form of Aramaic-Syriac and, like the Psalter, in poetic parallelism. Pointing to parallels with the Thanksgiving Hymns and other Qumran texts, he concludes that the Odist had probably been an Essene before he became a Christian, a member of the Johannine community.
This is an early Christian hymn book with 42 Odes. Reading it is kind of like reading the Book of Psalms, which works best in small doses, but I kind of bulldozed through it. Some of the odes contain references to a pre-existent state, #17 and #42 mention Christ freeing those trapped in spiritual prison, and some (like #19) speak of the Holy Spirit as a female, which is interesting. Ode #19 and a couple of others use the rather disturbing imagery of the Father feeding us with the metaphorical milk of his breasts.