Updated: Aug 4, 2019
100 Latin Hymns is not strictly an Orthodox Book, but there is much good Orthodox content within. Published by Harvard University in their Dumbarton Oaks Medieval Library, which publishes Medieval content in Old English, Latin and Greek. Like all in the series, the book is a bilingual text, containing the text of 100 Latin hymns, well known and more obscure, from the 3rd to 13th century. The hymns were translated and edited by Peter G. Walsh and Christopher Husch.
Although the scope of the book passes beyond the schism and, as a result, is not fully Orthodox, much of it, including a large selection of the works of St. Ambrose of Milan, very much is. Many of these prayers are quite beautiful, and, oddly, I have found an apologetic use for the book, as it allows me to easily demonstrate that the Church has venerated saints since the very beginning of its existence.
The Great schism is one of the greatest tragedies in the history of the Church. One of the less commonly mentioned repercussions of the schism, however, is that we have a tendency to forget that there was almost 1000 years of Western Orthodoxy before Rome's rebellion. The fount of Western spirituality, although now only a mere trickle, once flowed freely. We would all be wise to imbibe it.
St. Ambrose of Milan and all other Western saints, both well-remembered and long forgotten, pray for us.