Sir James George Frazer is perhaps best known for his collection of folklore and mythology, The Golden Bough, published in 1890. The work details legends and myths from many different cultures throughout history. Frazer theorized that human belief systems had begun as primitive magic, which was then replaced by religious dogma, which has now been replaced by scientific knowledge.
Frazer was perhaps one of the first anthropologists to analyze the link between myth and ritual ceremony. The Golden Bough is a study of legend and myth and how they are interpreted into ritual and celebration. Frazer's interpretation of the cycle of life, death and rebirth has carried on to this day, and in his work he explained that ultimately, this cycle is at the core of myths from every part of the globe.
For many modern Pagans, this book of folklore is a worthy thing to own, simply because it details religion and ritual from its early day, and follows the evolution of man's belief. If you plan on picking up a copy of The Golden Bough, get an unabridged edition, because it contains archeological support for Frazer's theories which was left out of the abridged version. It can be found at many used bookstores, and there are illustrated editions available.