Predicting if something is a code
I'm trying to help a non-mathematical friend by posting a question of his here. He studies literature and has come across a book which is written in a made-up language. The book is hundreds of pages, but apparently it is unknown if there is meaning behind what's written. Is there a standard way of predicting whether something like this is written in a code? Obviously we can't know for sure without actually decoding it, but are there some traits to look for? I have no idea, so I thought I would ask here. Thanks!
Here's the book in question: http://en.wikipedia.org/wiki/Codex_Seraphinianus