The Pet Shop

As mentioned in the "Symbols" section, the physical descriptions of the Pet Shop are pretty vague. In fact, we don't get to see what the Pet Shop looks like from the narrator's point of view at all; instead, he focuses on all the great animals:

THEN…
I saw a new kind!
And they were good, too!
How could I pick one?
Now what should we do? (17.1-5)

As a setting, the Pet Shop is left intentionally vague because it's supposed to be a playground for the kids' (and the readers') imaginations. At the Pet Shop, they can entertain all sorts of possibilities—both realistic and fantastical—and imagine what their lives would be like with all sorts of different pets.

Fun fact: The Pet Shop has a write-up over in the "Symbols" section, too, so for the full deets, get yourself over there, stat.