Like many people moving out of Christianity and into "alternative" spirituality, it was devotion to female Deities which first attracted me. As a child, I was drawn to Artemis and Athena (and Apollo). Through my teen years and into college, it was books about the Goddess and Goddesses which steadily filled my shelves, eventually overflowing. I was fascinated, enthralled by this idea of a female Deity, so different from the male Deity I had grown up honoring.
In graduate school, that overflowing pile turned into a landslide as Goddess Spirituality became the focus of my master's thesis. While I concentrated on the Fellowship of Isis (even making a pilgrimage to Clonegal Castle), I read broadly on the subject -- and it quickly became apparent that there is no one Goddess Spirituality. Goddess Spiritualities would be more accurate, as those who honor the Female Divine fall all along the spiritual spectrum, often touching different points simultaneously. Some devotees are monotheistic in their thealogy, believing in a single, all-encompassing female Deity. Others are more pantheistic or panentheistic, honoring nature and the female entity which created and manifests in it. Still others are henotheistic, acknowledging the existence of other Deities but choosing to honor only one (or a small handful). And there are devotees who identify as polytheistic, acknowledging and honoring multiple female Deities exclusively, or giving them priority over male Deities. Finally, there are strains of Goddess Spirituality running through progressive branches of Judaism and Christianity and (less visibly) Islam.
For those interested in practicing or becoming more familiar with Goddess Spirituality, there are lots and lots of books available. They range from heavy academic texts on ancient beliefs and rituals to translations of Gnostic Christian texts to modern Isian texts to archaeological reports to collections of poetry to modern fantasy and science fiction. Considering just how vast a topic this is, I'll focus here on my favorite nonfiction* texts, those I found most informative or which had the most impact on me.