A few weeks back I mentioned archive.org where a number of interesting and important liturgical books appeared - all free for download or online viewing in their entirety.
Here are a few more that may be of interest, particularly the first on the list:
The Divine Office : a study of the Roman Breviary (1920) by J.E. Quigley
Explanation of the construction, furniture and ornaments of a church, of the vestments of the clergy, and of the nature and ceremonies of the Mass (1834)
Hierurgia, or, The holy sacrifice of the Mass : with notes and dissertations elucidating its doctrines and ceremonies, and numerous illustrative plates (1833)
Notes on mediaeval services in England, with an index of Lincoln ceremonies (1898)
Handy manual of pontifical ceremonies (1904)
The externals of the Catholic church : her government, ceremonies, festivals, sacramentals, and devotions (1917)