When I was compiling the list of Universalist imprints you can download from Google, I came across an antique liturgical work that might appeal to those gathering up post-Christian resources, as Dan Harper has done.
While many today would find its style stilted and the project biased towards the Biblical religions -- Christianity and Judaism can be "ethical" but "Mohamadism" is "ethnic" -- there is a certain formality and dignity that has a continuing appeal. The project itself (I'm betting) would have attracted the Unitarians and Ethical Culturalists of the day. The copyright is 1900, so I'm wondering if this is a second edition, and if so, presumably the second edition of a popular first edition.
New York State Committee on Religion. A Book of Common Worship. New York: Knickerbocker Press, 1915.