If you are looking to buy books with the Armenian services in them, try St. Vartan Bookstore, at the Eastern Diocese in the U.S.:http://www.stvartanbookstore.com/index.asp
They have a large Divine Liturgy book for $25.00. The front part of the book translates the liturgy from Classical Armenian to Modern Armenian. The back part of the book transliterates the Classical Armenian and translates it into English. In my opinion, it should have been two different books.
They also have Nareg: Speaking with God from the Depth of the Heart
for $20.00. It is an English translation of the prayers written by St. Nareg about a thousand years ago. There is a website put up by one of the translators which deals with it: http://www.stgregoryofnarek.am/index.php
The prayers of Nareg are very beautiful devotional prayers. Unfortunately, there are some Armenians who treasure these prayers more as classical literature than as prayers to be said to God. The current translation was done by a linguist and a poet. I don't think a theologian was involved. In one prayer, the Armenian expression for Mother of God was translated into English as "madonna." In another prayer, they use the English pronoun "it" to refer to the Holy Spirit.
If you are interested in the services the priest does, like baptism, house blessings, weddings, etc., those are in a book the Armenians call "Mashdots." There is a pink paperback Mashdots which has both the Armenian and the English translation. It is $24.
There is also a white paperback Book of Hours or the Order of Common Prayers of the Armenian Apostolic Orthodox Church: Matins, Prime, Vespers and Occasional Offices
. I don't think it is in their website, but I know St. Vartan bookstore has it. You can e-mail them about it. Matins is done early every Sunday morning in the Armenian Church here in the U.S. However, unfortunately, Prime and Vespers are only done during Holy Lent. It is a pity. The Prime service is especially beautiful.
Hope this helps.