I think it's more a YA / older kids book.
story about a boy who thinks he is a cat. book has a lot of thoughtful stuff about how do we know who/what we are.
title might be something like daydreamer or daydreaming but googling this isn't helpful - there are lots of books with this in the title but none matching the subject matter.
no idea of author's name except vague impression that it contains the syllable an or ang as part of the name.
does this ring any bells for anyone?