It's a Book on NPR, or read a review of it (there are many, and they are favorable.) You might have even read it yourself (please do!) What prompted the discussion was the use of a single word--and here I am going to give away the punchline of the book, so if you don't want the wicked wit revealed.....SPOILER!
The conversation was prompted by Lane Smith's use of the word, "jackass." He uses the word twice: at the very beginning, when he is introducing the characters in the book, one of which is, indeed, a jackass. He uses it again, with much more dramatic effect at the very end, when Jackass is addressed by name. However, by the end of the book the reader has realized that Jackass is not just a donkey, but a fool as well, hence the comedic brilliance of that utterance.
To be honest, the books of Lane Smith beg the question--is sarcasm wasted on young readers? Perhaps 'sarcasm' is the wrong word for what I am trying to describe, which is closer to sophisticated, sly, sharp humor. If you revisit The Happy Hocky Family Moves to the Country (a personal favorite) or Glasses, Who Needs 'em? or even the much lauded John, Paul, George and Ben, there is a bite to these stories which rises above situational humor or visual jokes. Do young readers, 'get it'? Of course, as with any book, it depends on the reader. But in my opinion, why not test a child's wit? I've witnessed my own daughter, who at nine still laughs at burps, fling a zinger out every now and then. It's like she's using humor to test deeper intellectual waters. And in the end, isn't that what all great books do--challenge us intellectually?