Hekate is a complicated Goddess. Crossroads, entryways, and liminal spaces; journeys and war; the moon and the night and the underworld; ghosts and cemeteries; magic and herbology; pregnancy and midwifery and nursing; sailing and fishing and shepherding and dogs; all fall under her aegis. Honored originally in Anatolia, her worship spread throughout the Greek-speaking world. Adopted by the Romans (who tended to call her Hecate or Trivia), her worship spread even further. She is a major figure in the Theogony, the Homeric Hymn to Demeter, the Greek Magical Papyri, and the Chaldean Oracles. She even survived -- sort of -- the purging of the ancient pantheons and the conversion to Christianity as a hag figure in many folk tales and fairy tales. Today, she is honored by Pagans of many different traditions, ranging from Hellenismos to Religio to Wicca to unaffiliated, nondenominational Goddess worshippers.
It is, perhaps, not surprising that there are quite a few texts devoted to Hekate, as well as long chapters within other works. Helene P Foley's The Homeric Hymn to Demeter: Translation, Commentary, and Interpretive Essays, for instance.
For those who are curious about this Goddess, I can recommend several texts from my bookshelves. If you are looking for dense, solid academic work, there are two titles that should be at the top of your list: Restless Dead: Encounters Between the Living and the Dead in Ancient Greece; and Hekate Soteira: A Study of Hekate's Roles in the Chaldean Oracles and Related Literature; both by Sarah Iles Johnston. The former chronicles the evolution of Greek ideas about, and interactions with, the dead (with special attention paid to Hekate and the Erinyes), while the latter examines the evolution of ideas about Hekate herself, from Mother Goddess to mediating World Soul to Queen of Demons and Witches.