Reddit reviews Gender: The Key Concepts (Routledge Key Guides)

There's lots of critical terms books, and the "authoritative" book tends to vary from field to field.

If you legitimately want a primer, though, I've found Routledge Key Guides really helpful. There's one explicitly for Sociology, but I've also found the ones on Post-colonial Studies and Gender really useful. They're often taught in introductory college classes.