The entirety of What Pet Should I Get? has to do with the burden of choice, and so it makes sense that the title would sum up exactly what the narrator and Kay are struggling with: trying to decide what pet they should get.

Throughout the book, the two siblings keep asking each other the same question because they can't make up their minds. They go on looking through the whole inventory of pets (and then some) in order to find the answer to this question. Perhaps unsurprisingly, they resolve their problem at the very end of the book. In a twist, though, we don't know which pet they decide on.