The Mass of the Early Christians by Mike Aquila is a good source, as is the original Spirit of the Liturgy by Msgr. Romano Guardini, the precursor to the book of the same name written by Pope Benedict XVI.
I would also get my hands on books written by Dom Alcuin Reid, especially his work, The Organic Development of the Liturgy. You might also want to read the encyclical of Pope Pius XII, Mediator Dei. It offers some good insights on the Mass.