Pagan and Christian Creeds: Their Origin and Meaning

This is a comprehensive history that traces the development of various ancient religions and how they interlaced with Christianity.
From the intro:  "The subject of Religious Origins is a fascinating one, as the great multitude of books upon it, published in late years, tends to show. Indeed the great difficulty to-day in dealing with the subject, lies in the very mass of the material to hand—and that not only on account of the labor involved in sorting the material, but because the abundance itself of facts opens up temptation to a student in this department of Anthropology (as happens also in other branches of general Science) to rush in too hastily with what seems a plausible theory. The more facts, statistics, and so forth, there are available in any investigation, the easier it is to pick out a considerable number which will fit a given theory. The other facts being neglected or ignored, the views put forward enjoy for a time a great vogue. Then inevitably, and at a later time, new or neglected facts alter the outlook, and a new perspective is established.