Not sure how to rate this, so we'll say 3.5 for now, subject to possible rounding up later. I liked it, but if everything I like gets 4 stars then 4 doesn't mean much.
This book basically accomplishes what it sets out to do: it's funny and there's also thought put into the issues it examines. But I feel like it didn't try to do all that much with plot or character or worldbuilding, and if it had I would've liked it more.
At any rate, this is my first Discworld book (heresy in some quarters, that I've waited this long!) and based on this one I'd read more Pratchett.... but I'm not in any huge rush to do so.