The Penguin Dictionary of Religions (Dictionary, Penguin)

The Penguin Dictionary of Religions covers: religions throughout the world, including Buddhism, Christianity, Gnosticism, Hinduism, Islam, Jains, Judaism, and New Religious Movements; whole new sections, notably on religions in migration, Afro-Caribbean religious movements, modern North American developments, traditional religions in Latin America and Japanese New Religious Movements; and broad thematic issues, from migration and diaspora, gender and sexuality to mysticism and pilgrimage.
There is a full bibliography and index, as well as an invaluable breakdown of contents by subject area.