This is no Inception. Not even close. The last chapter of Holes actually ties everything up pretty nicely for the reader. The good get the goods and the bad, well, they get their comeuppance.
So far, so good. But our narrator isn't quite satisfied with happily ever after, is he? Let's take a look. In the last image of the book, we see Zero sitting with his mother (well, we assume it's his mom, at least), and this is how she is described:
She wasn't very old, but her skin had a weathered look to it, almost like leather. Her eyes seemed weary, as if she'd seen too many things in her life that she didn't want to see. (50.37)
We don't get any details about what Zero's mom has been up to since she left him at the park – all that is left to our imaginations. But what we do know is that she's clearly suffered a great deal: the record of it is quite literally written on her face. In all the happiness at the end of the book, Sachar makes sure that we can't forget just what it took for us to get here, and how messy life can really be.
From this point of view, it's important that we notice that that the very last words of the book are sung by Zero's mother, and that they're a revised version of the melancholy but hopeful lullaby that Madame Zeroni first taught to Elya Yelnats:
If only, if only, the moon speaks no reply;
Reflecting the sun and all that's gone by.
Be strong my weary wolf, turn around boldly.
Fly high, my baby bird,
My angel, my only. (50.39)
What do you think about the ending of Holes? Was it satisfying? If Sachar intentionally combines hope and sorrow at the close of the story, what do you think he's trying to tell us?