The Curious Incident of the Dog in the Night-Time (TCIotDitN-T) by Mark Haddon is a metafictional work ‘since the novel is shaped as the mystery story that Christopher was writing as a school project’ (https://blancosubio.wordpress.com/2008/01/29/metafiction/).
It comments on, or interacts with, other texts, or draws attention to their identity as literary artefacts (i.e. it has intertextuality) because ‘Christopher really likes Sherlock Holmes, and he constructs his own book as a murder mystery along the lines of one of Sir Arthur Conan Doyle’s stories. As such, he chooses a title similar to Doyle’s own, like “The Adventure of the Empty House,” or The Hound of the Baskervilles, which Christopher describes at length’ (https://www.shmoop.com/curious-incident/title.html).
So there you have it; two meaty quotes from the internet that prove that TCIotDitN-T has elements of both metafiction and intertextuality.
I could add all sorts of extraneous matter like that fact that I really enjoyed the book and that I have a liking for fiction (and fact) about Asperger’s Syndrome and that I saw the stage-play (not as good as the book) or that I have a little bit of Christopher in me (no, not a reference to cannibalism) but at the end of the day (like what it is here) it’s pollen-season and my eyes are itching and I just want to go to bed now, so you’ll have to assume I know loads and loads about the subject and just let me leave it at that.