Peter Aczel. An Introduction to Inductive Definitions. In Handbook of Mathematical Logic, 1977.

Fritz mentioned referred to this as a primer on inductive definitions, inference rules, and the like. I had seen it before but passed it up as too dense; now that I’m reading it, I like Aczel’s presentation. Although the low exposition-to-definition ratio reminds me of my old real analysis textbook.

Sorry for the ScienceDirect link.

EDIT: Oy, okay, my brain can’t handle sections 2-4. Section 1 was a good read, though.