The Curious Incident of the Dog in the Night-Time has an awesome ending that reminds us of the introduction. That's what we call some satisfying symmetry. We wouldn't expect anything less from someone as math-loving as our narrator, though. What we might not expect is the pretty red bow with which he wraps it up.
To be sure, it's a very happy ending, but it actually comes as a bit of a surprise. Things had been getting worse and worse for Christopher for the whole second half of the book, and then with only a few pages from the end, things still aren't looking so good. He writes, "there were more bad things than good things" (233.137). Among them, Toby dies. (RIP Toby. We hardly knew ye.)
But then everything turns around in pretty short order. What's the catalyst for such a change? Well, let's see. Christopher's father makes yet another heart-wrenching apology, which totally doesn't move Christopher. But then… he buys him a puppy! And Christopher is very, very happy about that. The puppy will have to live with Christopher's father (his mom's place is too small), so that will presumably help them reconnect.
Then Christopher finds out that he got the highest possible grade on his exam. In the months that follow, he begins planting a garden with his father, and studying for the next big math exam. More than anything, though, what makes the ending so joyous, and pretty inspirational, is Christopher's final reflection on his adventure in the book's final sentence:
And I know I can do this because I went to London on my own, and because I solved the mystery of Who Killed Wellington? And I found my mother and I was brave and I wrote a book and that means I can do anything. (233.170)
A fine ending, indeed.