I actually think Radical Focus is a quick and good read for getting the gist. Wodtke writes a fictional account of a start-up learning (and failing) to use OKRs. It’s an effective way to get the point across and way more interesting than the typical “how to” sort of text.
I also have a close friend, an engineer who was the director of an art museum and is now running her own non-profit, who uses them religiously and I’m able to understand their value through her example.