No, that title is not a typo. I do mean theoilogy.
Theology, to quote the ever-handy Wikipedia, derives "from Ancient Greek Θεός meaning "God" and λόγος, -logy, meaning "study of." God. Singular. By its very nature, at its very root, the word assumes a single Godhead. As such, I find the term best suited only to those religious systems which are explicitly monotheistic or monistic, eg Islam, most strains of Christianity, some branches of Judaism, and some sects within Hinduism.*
But, it is an ill-fit with explicitly polytheistic or even duotheistic systems, such as some branches of Judaism, some Christian sects, most sects within Hinduism, and the majority of Pagan and indigenous traditions. When I write about the nature of Zeus, I am not engaging in theology -- I am engaging in theoilogy. Zeus is not God Alone. He is part of a vast family of Deities; He is part of a web of relationships and responsibilities, and I cannot even begin to comprehend him outside of that web. Thus, theoilogy, from the Ancient Greek Θεοί meaning "Gods." Plural.