The story is straightforward and easy to understand, with down-to-earth language and metaphors. Here's an example:
In the middle of the night, when the rain stopped, Pelayo and Elisenda were still killing crabs. A short time afterward the child woke up without a fever and with a desire to eat. (4)
We've got nice concrete words—"night," "rain," "crabs," "fever," and "eat"—and a simple, if bizarre, scenario. Sick kid; crabs to kill. The only tough part about this book might be swallowing the way the characters react to the totally crazy fact of a man with wings.