The Service for the Lord's Day - Westminster Press - ISBN 0-664-24643-5 Not only does this give you the current Presbyterian Liturgy but includes a fine commentary on the history and thoughts behind it alongside excellent suggestions for further reading.
The Story of Christian Music - Andrew Wilson-Dickson - Lion Publishing ISBN 0-7459-2142-6 A comprehensive survey of the musical side of the churches musical development that takes you on a journey through music in ancient Israel, Gregorian Chant, Salvation Army Brass Bands, Vaughan Williams, Bach, African Music, and every where in between. Excellent.