This book was pretending to be silly for maybe even the first...third of it?
It is not a silly book. It's a Peter S. Beagle book so, somewhat by definition, it has a extraordinary amount of heart and also that heart is bleeding.
How dare you emotionally skewer me with stories about humanity and identity? Again? 
It's not The Last Unicorn so don't go in expecting that. 
But it does...rhyme in the way it asks its characters to know themselves and just keeps asking until there is nothing left but the answer.